text:
**[GitLab Flavored Markdown](#gitlab-flavored-markdown-gfm)**

* [Newlines](#newlines)
* [Multiple underscores in words](#multiple-underscores-in-words)
* [URL auto-linking](#url-auto-linking)
* [Code and Syntax Highlighting](#code-and-syntax-highlighting)
* [Emoji](#emoji)
* [Special GitLab references](#special-gitlab-references)
* [Task lists](#task-lists)

**[Standard Markdown](#standard-markdown)**

* [Headers](#headers)
* [Emphasis](#emphasis)
* [Lists](#lists)
* [Links](#links)
* [Images](#images)
* [Blockquotes](#blockquotes)
* [Inline HTML](#inline-html)
* [Horizontal Rule](#horizontal-rule)
* [Line Breaks](#line-breaks)
* [Tables](#tables)

**[References](#references)**

## GitLab Flavored Markdown (GFM)

For GitLab we developed something we call "GitLab Flavored Markdown" (GFM). It extends the standard Markdown in a few significant ways to add some useful functionality.

You can use GFM in

- commit messages
- comments
- issues
- merge requests
- milestones
- wiki pages

You can also use other rich text files in GitLab. You might have to install a dependency to do so. Please see the [github-markup gem readme](https://github.com/gitlabhq/markup#markups) for more information.

## Newlines

GFM honors the markdown specification in how [paragraphs and line breaks are handled](http://daringfireball.net/projects/markdown/syntax#p).

A paragraph is simply one or more consecutive lines of text, separated by one or more blank lines.
Line-breaks, or softreturns, are rendered if you end a line with two or more spaces

    Roses are red [followed by two or more spaces]
    Violets are blue

    Sugar is sweet

Roses are red
Violets are blue

Sugar is sweet

## Multiple underscores in words

It is not reasonable to italicize just _part_ of a word, especially when you're dealing with code and names that often appear with multiple underscores. Therefore, GFM ignores multiple underscores in words.

    perform_complicated_task
    do_this_and_do_that_and_another_thing

perform_complicated_task
do_this_and_do_that_and_another_thing

## URL auto-linking

GFM will autolink almost any URL you copy and paste into your text.

    * http://www.google.com
    * https://google.com/
    * ftp://ftp.us.debian.org/debian/
    * smb://foo/bar/baz
    * irc://irc.freenode.net/gitlab
    * http://localhost:3000

* http://www.google.com
* https://google.com/
* ftp://ftp.us.debian.org/debian/
* smb://foo/bar/baz
* irc://irc.freenode.net/gitlab
* http://localhost:3000

## Code and Syntax Highlighting

Blocks of code are either fenced by lines with three back-ticks ```</code>, or are indented with four spaces. Only the fenced code blocks support syntax highlighting.

```no-highlight
Inline `code` has `back-ticks around` it.
```

Inline `code` has `back-ticks around` it.

Example:

    ```javascript
    var s = "JavaScript syntax highlighting";
    alert(s);
    ```

    ```python
    def function():
        #indenting works just fine in the fenced code block
        s = "Python syntax highlighting"
        print s
    ```

    ```ruby
    require 'redcarpet'
    markdown = Redcarpet.new("Hello World!")
    puts markdown.to_html
    ```

    ```
    No language indicated, so no syntax highlighting.
    s = "There is no highlighting for this."
    But let's throw in a tag.
    ```

becomes:

```javascript
var s = "JavaScript syntax highlighting";
alert(s);
```

```python
def function():
    #indenting works just fine in the fenced code block
    s = "Python syntax highlighting"
    print s
```

```ruby
require 'redcarpet'
markdown = Redcarpet.new("Hello World!")
puts markdown.to_html
```

```
No language indicated, so no syntax highlighting.
s = "There is no highlighting for this."
But let's throw in a tag.
```

## Emoji

	Sometimes you want to :monkey: around a bit and add some :star2: to your :speech_balloon:. Well we have a gift for you:

	:zap: You can use emoji anywhere GFM is supported. :v:

	You can use it to point out a :bug: or warn about :speak_no_evil: patches. And if someone improves your really :snail: code, send them some :birthday:. People will :heart: you for that.

	If you are new to this, don't be :fearful:. You can easily join the emoji :family:. All you need to do is to look up on the supported codes.

	Consult the [Emoji Cheat Sheet](http://emoji.codes) for a list of all supported emoji codes. :thumbsup:

Sometimes you want to :monkey: around a bit and add some :star2: to your :speech_balloon:. Well we have a gift for you:

:zap: You can use emoji anywhere GFM is supported. :v:

You can use it to point out a :bug: or warn about :speak_no_evil: patches. And if someone improves your really :snail: code, send them some :birthday:. People will :heart: you for that.

If you are new to this, don't be :fearful:. You can easily join the emoji :family:. All you need to do is to look up on the supported codes.

Consult the [Emoji Cheat Sheet](http://emoji.codes) for a list of all supported emoji codes. :thumbsup:

## Special GitLab References

GFM recognizes special references.

You can easily reference e.g. an issue, a commit, a team member or even the whole team within a project.

GFM will turn that reference into a link so you can navigate between them easily.

GFM will recognize the following:

| input                  | references                 |
|:-----------------------|:---------------------------|
| `@user_name`           | specific user              |
| `@group_name`          | specific group             |
| `@all`                 | entire team                |
| `#123`                 | issue                      |
| `!123`                 | merge request              |
| `$123`                 | snippet                    |
| `~123`                 | label by ID                |
| `~bug`                 | one-word label by name     |
| `~"feature request"`   | multi-word label by name   |
| `9ba12248`             | specific commit            |
| `9ba12248...b19a04f5`  | commit range comparison    |
| `[README](doc/README)` | repository file references |

GFM also recognizes certain cross-project references:

| input                                   | references              |
|:----------------------------------------|:------------------------|
| `namespace/project#123`                 | issue                   |
| `namespace/project!123`                 | merge request           |
| `namespace/project$123`                 | snippet                 |
| `namespace/project@9ba12248`            | specific commit         |
| `namespace/project@9ba12248...b19a04f5` | commit range comparison |

## Task Lists

You can add task lists to issues, merge requests and comments. To create a task list, add a specially-formatted Markdown list, like so:

```no-highlight
- [x] Completed task
- [ ] Incomplete task
    - [ ] Sub-task 1
    - [x] Sub-task 2
    - [ ] Sub-task 3
```

- [x] Completed task
- [ ] Incomplete task
    - [ ] Sub-task 1
    - [x] Sub-task 2
    - [ ] Sub-task 3

Task lists can only be created in descriptions, not in titles. Task item state can be managed by editing the description's Markdown or by toggling the rendered check boxes.

# Standard Markdown

## Headers

```no-highlight
# H1
## H2
### H3
#### H4
##### H5
###### H6

Alternatively, for H1 and H2, an underline-ish style:

Alt-H1
======

Alt-H2
------
```

# H1
## H2
### H3
#### H4
##### H5
###### H6

Alternatively, for H1 and H2, an underline-ish style:

Alt-H1
======

Alt-H2
------

### Header IDs and links

All Markdown-rendered headers automatically get IDs, except in comments.

On hover a link to those IDs becomes visible to make it easier to copy the link to the header to give it to someone else.

The IDs are generated from the content of the header according to the following rules:

1. All text is converted to lowercase
1. All non-word text (e.g., punctuation, HTML) is removed
1. All spaces are converted to hyphens
1. Two or more hyphens in a row are converted to one
1. If a header with the same ID has already been generated, a unique
   incrementing number is appended.

For example:

```
# This header has spaces in it
## This header has a :thumbsup: in it
# This header has Unicode in it: 한글
## This header has spaces in it
### This header has spaces in it
```

Would generate the following link IDs:

1. `this-header-has-spaces-in-it`
1. `this-header-has-a-in-it`
1. `this-header-has-unicode-in-it-한글`
1. `this-header-has-spaces-in-it-1`
1. `this-header-has-spaces-in-it-2`

Note that the Emoji processing happens before the header IDs are generated, so the Emoji is converted to an image which then gets removed from the ID.

## Emphasis

```no-highlight
Emphasis, aka italics, with *asterisks* or _underscores_.

Strong emphasis, aka bold, with **asterisks** or __underscores__.

Combined emphasis with **asterisks and _underscores_**.

Strikethrough uses two tildes. ~~Scratch this.~~
```

Emphasis, aka italics, with *asterisks* or _underscores_.

Strong emphasis, aka bold, with **asterisks** or __underscores__.

Combined emphasis with **asterisks and _underscores_**.

Strikethrough uses two tildes. ~~Scratch this.~~

## Lists

```no-highlight
1. First ordered list item
2. Another item
  * Unordered sub-list.
1. Actual numbers don't matter, just that it's a number
  1. Ordered sub-list
4. And another item.

* Unordered list can use asterisks
- Or minuses
+ Or pluses
```

1. First ordered list item
2. Another item
  * Unordered sub-list.
1. Actual numbers don't matter, just that it's a number
  1. Ordered sub-list
4. And another item.

* Unordered list can use asterisks
- Or minuses
+ Or pluses

If a list item contains multiple paragraphs,
each subsequent paragraph should be indented with four spaces.

```no-highlight
1.  First ordered list item

    Second paragraph of first item.
2.  Another item
```

1.  First ordered list item

    Second paragraph of first item.
2.  Another item

If the second paragraph isn't indented with four spaces,
the second list item will be incorrectly labeled as `1`.

```no-highlight
1. First ordered list item

   Second paragraph of first item.
2. Another item
```

1. First ordered list item

   Second paragraph of first item.
2. Another item

## Links

There are two ways to create links, inline-style and reference-style.

    [I'm an inline-style link](https://www.google.com)

    [I'm a reference-style link][Arbitrary case-insensitive reference text]

    [I'm a relative reference to a repository file](LICENSE)

    [You can use numbers for reference-style link definitions][1]

    Or leave it empty and use the [link text itself][]

    Some text to show that the reference links can follow later.

    [arbitrary case-insensitive reference text]: https://www.mozilla.org
    [1]: http://slashdot.org
    [link text itself]: http://www.reddit.com

[I'm an inline-style link](https://www.google.com)

[I'm a reference-style link][Arbitrary case-insensitive reference text]

[I'm a relative reference to a repository file](LICENSE)

[You can use numbers for reference-style link definitions][1]

Or leave it empty and use the [link text itself][]

Some text to show that the reference links can follow later.

[arbitrary case-insensitive reference text]: https://www.mozilla.org
[1]: http://slashdot.org
[link text itself]: http://www.reddit.com

**Note**

Relative links do not allow referencing project files in a wiki page or wiki page in a project file. The reason for this is that, in GitLab, wiki is always a separate git repository. For example:

`[I'm a reference-style link](style)`

will point the link to `wikis/style` when the link is inside of a wiki markdown file.

## Images

    Here's our logo (hover to see the title text):

    Inline-style:
    ![alt text](assets/logo-white.png)

    Reference-style:
    ![alt text1][logo]

    [logo]: assets/logo-white.png

Here's our logo:

Inline-style:

![alt text](/assets/logo-white.png)

Reference-style:

![alt text][logo]

[logo]: /assets/logo-white.png

## Blockquotes

```no-highlight
> Blockquotes are very handy in email to emulate reply text.
> This line is part of the same quote.

Quote break.

> This is a very long line that will still be quoted properly when it wraps. Oh boy let's keep writing to make sure this is long enough to actually wrap for everyone. Oh, you can *put* **Markdown** into a blockquote.
```

> Blockquotes are very handy in email to emulate reply text.
> This line is part of the same quote.

Quote break.

> This is a very long line that will still be quoted properly when it wraps. Oh boy let's keep writing to make sure this is long enough to actually wrap for everyone. Oh, you can *put* **Markdown** into a blockquote.

## Inline HTML

You can also use raw HTML in your Markdown, and it'll mostly work pretty well.

See the documentation for HTML::Pipeline's [SanitizationFilter](http://www.rubydoc.info/gems/html-pipeline/HTML/Pipeline/SanitizationFilter#WHITELIST-constant) class for the list of allowed HTML tags and attributes.  In addition to the default `SanitizationFilter` whitelist, GitLab allows `span` elements.

```no-highlight

Definition list

Is something people use sometimes.

Markdown in HTML

Does *not* work **very** well. Use HTML tags.

```

<dl>
  <dt>Definition list</dt>
  <dd>Is something people use sometimes.</dd>

  <dt>Markdown in HTML</dt>
  <dd>Does *not* work **very** well. Use HTML <em>tags</em>.</dd>
</dl>

## Horizontal Rule

```
Three or more...

---

Hyphens

***

Asterisks

___

Underscores
```

Three or more...

---

Hyphens

***

Asterisks

___

Underscores

## Line Breaks

My basic recommendation for learning how line breaks work is to experiment and discover -- hit <Enter> once (i.e., insert one newline), then hit it twice (i.e., insert two newlines), see what happens. You'll soon learn to get what you want. "Markdown Toggle" is your friend.

Here are some things to try out:

```
Here's a line for us to start with.

This line is separated from the one above by two newlines, so it will be a *separate paragraph*.

This line is also a separate paragraph, but...
This line is only separated by a single newline, so it's a separate line in the *same paragraph*.

This line is also a separate paragraph, and...
This line is on its own line, because the previous line ends with two
spaces.
```

Here's a line for us to start with.

This line is separated from the one above by two newlines, so it will be a *separate paragraph*.

This line is also begins a separate paragraph, but...
This line is only separated by a single newline, so it's a separate line in the *same paragraph*.

This line is also a separate paragraph, and...
This line is on its own line, because the previous line ends with two
spaces.

## Tables

Tables aren't part of the core Markdown spec, but they are part of GFM and Markdown Here supports them.

```
| header 1 | header 2 |
| -------- | -------- |
| cell 1   | cell 2   |
| cell 3   | cell 4   |
```

Code above produces next output:

| header 1 | header 2 |
| -------- | -------- |
| cell 1   | cell 2   |
| cell 3   | cell 4   |

**Note**

The row of dashes between the table header and body must have at least three dashes in each column.

By including colons in the header row, you can align the text within that column:

```
| Left Aligned | Centered | Right Aligned | Left Aligned | Centered | Right Aligned |
| :----------- | :------: | ------------: | :----------- | :------: | ------------: |
| Cell 1       | Cell 2   | Cell 3        | Cell 4       | Cell 5   | Cell 6        |
| Cell 7       | Cell 8   | Cell 9        | Cell 10      | Cell 11  | Cell 12       |
```

| Left Aligned | Centered | Right Aligned | Left Aligned | Centered | Right Aligned |
| :----------- | :------: | ------------: | :----------- | :------: | ------------: |
| Cell 1       | Cell 2   | Cell 3        | Cell 4       | Cell 5   | Cell 6        |
| Cell 7       | Cell 8   | Cell 9        | Cell 10      | Cell 11  | Cell 12       |

## References

- This document leveraged heavily from the [Markdown-Cheatsheet](https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet).
- The [Markdown Syntax Guide](http://daringfireball.net/projects/markdown/syntax) at Daring Fireball is an excellent resource for a detailed explanation of standard markdown.
- [Dillinger.io](http://dillinger.io) is a handy tool for testing standard markdown.


text:
'*******************************************************************************************'
'                                                                                '
' Download Free Evaluation Version From:     https://bytescout.com/download/web-installer   '
'                                                                                '
' Also available as Web API! Get free API Key https://app.pdf.co/signup                     '
'                                                                                '
' Copyright © 2017-2020 ByteScout, Inc. All rights reserved.                                '
' https://www.bytescout.com                                                                 '
' https://www.pdf.co                                                                        '
'*******************************************************************************************'

Imports System.IO
Imports System.Threading
Imports Bytescout.PDFExtractor

Module Module1

    ' Limit to 4 threads in queue.
    ' Set this value to number of your processor cores for max performance.
    ReadOnly ThreadLimiter As Semaphore = New Semaphore(4, 4)

    <MTAThread()>
    Sub Main()

        ' Get all PDF files in a folder
        Dim files = Directory.GetFiles("..\..\..\..\", "*.pdf")
        ' Array of events to wait
        Dim doneEvents(files.Length - 1) As ManualResetEvent

        For i As Integer = 0 To files.Length - 1

            ' Wait for the queue
            ThreadLimiter.WaitOne()

            ' Start thread with filename and event in params
            doneEvents(i) = New ManualResetEvent(False)
            Dim threadData As Object = New Object() {files(i), doneEvents(i)}
            ThreadPool.QueueUserWorkItem(AddressOf ConvertPdfToTxt, threadData)

        Next

        ' Wait until all threads finish
        WaitHandle.WaitAll(doneEvents)

        Console.WriteLine()
        Console.WriteLine("All is done.")
        Console.WriteLine()
        Console.WriteLine("Press any key to exit...")
        Console.ReadKey()

    End Sub

    Private Sub ConvertPdfToTxt(ByVal state As Object)

        ' Get filename and event from params
        Dim file As String = state(0)
        Dim doneEvent As ManualResetEvent = state(1)

        Dim resultFileName = Path.GetFileName(file) + ".txt"

        Try

            Console.WriteLine("Converting " + file)

            Using extractor As New TextExtractor("demo", "demo")

                extractor.LoadDocumentFromFile(file)
                extractor.SaveTextToFile(resultFileName)

            End Using

            Console.WriteLine("Finished " + resultFileName)

        Finally

            ' Signal the thread is finished
            doneEvent.Set()
            ' Release semaphore
            ThreadLimiter.Release()

        End Try

    End Sub

End Module

redpajama_set_name: RedPajamaGithub


text:
//------------------------------------------------------------------------------
// <copyright file="SqlCacheDepModule.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//------------------------------------------------------------------------------

namespace System.Web.Caching {

    using System;
    using System.Threading;
    using System.Collections;
    using System.Configuration;
    using System.IO;
    using System.Web.Caching;
    using System.Web.Util;
    using System.Web.Configuration;
    using System.Xml;
    using System.Data;
    using System.Data.SqlClient;
    using System.Globalization;
    using System.Security.Permissions;
    using System.Text;
    using System.Runtime.InteropServices;
    using System.EnterpriseServices;
    using System.Web.UI;
    using System.Web.DataAccess;
    using System.Security.Principal;
    using System.Web.Hosting;
    using System.Runtime.Serialization;
    using System.Web.Management;
    using System.Security;

    public sealed class SqlCacheDependency : CacheDependency {

        internal static bool        s_hasSqlClientPermission;
        internal static bool        s_hasSqlClientPermissionInited;

        const string SQL9_CACHE_DEPENDENCY_DIRECTIVE = "CommandNotification";
        internal const string SQL9_OUTPUT_CACHE_DEPENDENCY_COOKIE = "MS.SqlDependencyCookie";

        SqlDependency       _sqlYukonDep;       // SqlDependency for Yukon
        DatabaseNotifState  _sql7DatabaseState;     // Database state for SQL7/2000
        string              _uniqueID;              // used by HttpCachePolicy for the ETag
#if DBG
        bool                _isUniqueIDInitialized;
#endif

        struct Sql7DependencyInfo {
            internal string  _database;
            internal string  _table;
        }

        // For generating Unique Id
        Sql7DependencyInfo  _sql7DepInfo;
        int                 _sql7ChangeId;

        // For Non-SQL9 SQL servers, we create a dependency based on an internal cached item.

        public SqlCacheDependency(string databaseEntryName, string tableName)
        :base(0, null, new string[1] {GetDependKey(databaseEntryName, tableName)})
        {
            Debug.Trace("SqlCacheDependency",
                            "Depend on key=" + GetDependKey(databaseEntryName, tableName) + "; value=" +
                            HttpRuntime.CacheInternal[GetDependKey(databaseEntryName, tableName)]);

            // Permission checking is done in GetDependKey()

            _sql7DatabaseState = SqlCacheDependencyManager.AddRef(databaseEntryName);
            _sql7DepInfo._database = databaseEntryName;
            _sql7DepInfo._table = tableName;

            object o = HttpRuntime.CacheInternal[GetDependKey(databaseEntryName, tableName)];
            if (o == null) {
                // If the cache entry can't be found, this cache dependency will be set to CHANGED already.
                _sql7ChangeId = -1;
            }
            else {
                // Note that if the value in the cache changed between the base ctor and here, even though
                // we get a wrong unqiue Id, but it's okay because that change will cause the CacheDependency's
                // state to become CHANGED and any cache operation using this CacheDependency will fail anyway.
                _sql7ChangeId = (int)o;
            }

            // The ctor of every class derived from CacheDependency must call this.
            FinishInit();

            InitUniqueID();
        }

        protected override void DependencyDispose() {
            if (_sql7DatabaseState != null) {
                SqlCacheDependencyManager.Release(_sql7DatabaseState);
            }
        }

        // For SQL9, we use SqlDependency
        public SqlCacheDependency(SqlCommand sqlCmd) {
            HttpContext context = HttpContext.Current;

            if (sqlCmd == null) {
                throw new ArgumentNullException("sqlCmd");
            }

            // Prevent a conflict between using SQL9 outputcache and an explicit
            // SQL9 SqlCacheDependency at the same time.  See VSWhidey 396429 and
            // the attached email in the bug.
            if (context != null && context.SqlDependencyCookie != null &&  // That means We have already setup SQL9 dependency for output cache
                sqlCmd.NotificationAutoEnlist) {    // This command will auto-enlist in that output cache dependency
                throw new HttpException(SR.GetString(SR.SqlCacheDependency_OutputCache_Conflict));
            }

            CreateSqlDep(sqlCmd);

            InitUniqueID();
        }

        void InitUniqueID() {
            if (_sqlYukonDep != null) {
                // Yukon does not provide us with an ID, so we'll use a Guid.
                _uniqueID = Guid.NewGuid().ToString("N", CultureInfo.InvariantCulture);
            }
            else if (_sql7ChangeId == -1) {
                // The database/tablen entry can't be found in the cache.  That means SQL doesn't have
                // this database/table registered for sql cache dependency.  In this case, we can't
                // generate a unique id.
                _uniqueID = null;
            }
            else {
                _uniqueID = _sql7DepInfo._database + ":" + _sql7DepInfo._table + ":" + _sql7ChangeId.ToString(CultureInfo.InvariantCulture);
            }
#if DBG
            _isUniqueIDInitialized = true;
#endif
        }

        public override string GetUniqueID() {
#if DBG
            Debug.Assert(_isUniqueIDInitialized == true, "_isUniqueIDInitialized == true");
#endif
            return _uniqueID;
        }

        private static void CheckPermission() {
            if (!s_hasSqlClientPermissionInited) {
                if (!System.Web.Hosting.HostingEnvironment.IsHosted) {
                    try {
                        new SqlClientPermission(PermissionState.Unrestricted).Demand();
                        s_hasSqlClientPermission = true;
                    }
                    catch (SecurityException) {}
                }
                else {
                    s_hasSqlClientPermission = Permission.HasSqlClientPermission();
                }

                s_hasSqlClientPermissionInited = true;
            }

            if (!s_hasSqlClientPermission) {
                throw new HttpException(SR.GetString(SR.SqlCacheDependency_permission_denied));
            }
        }

        void OnSQL9SqlDependencyChanged(Object sender, SqlNotificationEventArgs e) {
            Debug.Trace("SqlCacheDependency", "SQL9 dependency changed: depId=" + _sqlYukonDep.Id);
            NotifyDependencyChanged(sender, e);
        }

        private SqlCacheDependency() {
            CreateSqlDep(null);
            InitUniqueID();
        }

        void CreateSqlDep(SqlCommand sqlCmd) {
            _sqlYukonDep = new SqlDependency();

            // Note: sqlCmd is null in output cache case.

            if (sqlCmd != null) {
                Debug.Trace("SqlCacheDependency", "SqlCmd added to SqlDependency object");
                _sqlYukonDep.AddCommandDependency(sqlCmd);
            }

            _sqlYukonDep.OnChange += new OnChangeEventHandler(OnSQL9SqlDependencyChanged);

            Debug.Trace("SqlCacheDependency", "SQL9 dependency created: depId=" + _sqlYukonDep.Id);
        }

        internal static void ValidateOutputCacheDependencyString(string depString, bool page) {
            if (depString == null) {
                throw new HttpException(SR.GetString(SR.Invalid_sqlDependency_argument, depString));
            }

            if (StringUtil.EqualsIgnoreCase(depString, SQL9_CACHE_DEPENDENCY_DIRECTIVE)) {
                if (!page) {
                    // It's impossible for only a page, but not its controls, to use Yukon Cache Dependency; neither
                    // can the opposite scenario possible.  It's because once we create a SqlDependency and
                    // stick it to the context, it's complicated (but not impossible) to clear it when rendering
                    // the parts (either a page or a control) that doesn't depend on Yukon.
                    // To keep things simple, we restrict Yukon Cache Dependency only to page.
                    throw new HttpException(
                        SR.GetString(SR.Attrib_Sql9_not_allowed));
                }
            }
            else {
                // It's for non-SQL 9 scenario.
                ParseSql7OutputCacheDependency(depString);
            }
        }

        public static CacheDependency CreateOutputCacheDependency(string dependency) {
            if (dependency == null) {
                throw new HttpException(SR.GetString(SR.Invalid_sqlDependency_argument, dependency));
            }

            if (StringUtil.EqualsIgnoreCase(dependency, SQL9_CACHE_DEPENDENCY_DIRECTIVE)) {
                HttpContext context = HttpContext.Current;
                Debug.Assert(context != null);

                SqlCacheDependency  dep = new SqlCacheDependency();

                Debug.Trace("SqlCacheDependency", "Setting depId=" + dep._sqlYukonDep.Id);
                context.SqlDependencyCookie = dep._sqlYukonDep.Id;

                return dep;
            }
            else {
                ArrayList                   sqlDependencies;
                AggregateCacheDependency    aggr = null;
                Sql7DependencyInfo           info;

                sqlDependencies = ParseSql7OutputCacheDependency(dependency);

                // ParseSql7OutputCacheDependency will throw if we cannot find a single entry
                Debug.Assert(sqlDependencies.Count > 0, "sqlDependencies.Count > 0");

                Debug.Trace("SqlCacheDependency", "Creating SqlCacheDependency for SQL8 output cache");

                if (sqlDependencies.Count == 1) {
                    info = (Sql7DependencyInfo)sqlDependencies[0];
                    return CreateSql7SqlCacheDependencyForOutputCache(info._database, info._table, dependency);
                }

                aggr = new AggregateCacheDependency();

                for(int i=0; i < sqlDependencies.Count; i++) {
                    info = (Sql7DependencyInfo)sqlDependencies[i];
                    aggr.Add(CreateSql7SqlCacheDependencyForOutputCache(info._database, info._table, dependency));
                }

                return aggr;
            }
        }

        static SqlCacheDependency CreateSql7SqlCacheDependencyForOutputCache(string database, string table, string depString) {
            try {
                return new SqlCacheDependency(database, table);
            }
            catch (HttpException e) {
                HttpException outerException = new HttpException(
                       SR.GetString(SR.Invalid_sqlDependency_argument2, depString, e.Message), e);

                outerException.SetFormatter(new UseLastUnhandledErrorFormatter(outerException));

                throw outerException;
            }
        }

        static string GetDependKey(string database, string tableName) {

            // This is called by ctor SqlCacheDependency(string databaseEntryName, string tableName)
            // before the body of that ctor is executed.  So we have to make sure the app has
            // the right permission here.
            CheckPermission();

            // First is to check whether Sql cache polling is enabled in config or not.
            if (database == null) {
                throw new ArgumentNullException("database");
            }

            if (tableName == null) {
                throw new ArgumentNullException("tableName");
            }

            if (tableName.Length == 0) {
                throw new ArgumentException(SR.GetString(SR.Cache_null_table));
            }

            string  monitorKey = SqlCacheDependencyManager.GetMoniterKey(database, tableName);

            // Make sure the table is already registered with the database and
            // we've polled the database at least once, so that there is an
            // entry in the cache.
            SqlCacheDependencyManager.EnsureTableIsRegisteredAndPolled(database, tableName);
            return monitorKey;
        }

        static string VerifyAndRemoveEscapeCharacters(string s) {
            int     i;
            bool    escape = false;

            for (i=0; i < s.Length; i++) {
                if (escape) {
                    if (s[i] != '\\' && s[i] != ':' && s[i] != ';') {
                        // Only '\\', '\:' and '\;' are allowed
                        throw new ArgumentException();
                    }
                    escape = false;
                    continue;
                }

                if (s[i] == '\\') {
                    if (i+1 == s.Length) {
                        // No character following escape char
                        throw new ArgumentException();
                    }
                    escape = true;
                    s = s.Remove(i, 1);
                    i--;
                }
            }

            return s;
        }

        internal static ArrayList ParseSql7OutputCacheDependency(string outputCacheString) {
            // The database and the table name are separated by a ":".  If the name
            // contains a ":" character, specify it by doing "\:"
            // Pairs of entries are separated by a ";"
            bool        escape = false;
            int         iDatabaseStart = 0;
            int         iTableStart = -1;
            string      database = null;        // The database portion of the pair
            ArrayList   dependencies = null;
            int         len;
            Sql7DependencyInfo   info;

            try {
                for (int i = 0; i < outputCacheString.Length+1; i++) {
                    if (escape) {
                        escape = false;
                        continue;
                    }

                    if (i != outputCacheString.Length && outputCacheString[i] == '\\') {
                        escape = true;
                        continue;
                    }

                    // We have reached ';' or the end of the string
                    if (i == outputCacheString.Length || outputCacheString[i] == ';' ) {
                        if (database==null) {
                            // No database name
                            throw new ArgumentException();
                        }

                        // Get the lenght of the table portion
                        len = i - iTableStart;
                        if (len == 0) {
                            // No table name
                            throw new ArgumentException();
                        }

                        info = new Sql7DependencyInfo();
                        info._database = VerifyAndRemoveEscapeCharacters(database);
                        info._table = VerifyAndRemoveEscapeCharacters(outputCacheString.Substring(iTableStart, len));

                        if (dependencies == null) {
                            dependencies = new ArrayList(1);
                        }

                        dependencies.Add(info);

                        // Reset below values.  We are searching for the next pair.
                        iDatabaseStart = i+1;
                        database = null;
                    }

                    // Have we reached the end of the string?
                    if (i == outputCacheString.Length) {
                        break;
                    }

                    if (outputCacheString[i] == ':') {
                        if (database != null) {
                            // We have already got the database portion
                            throw new ArgumentException();
                        }

                        // Do we get the database part?
                        len = i - iDatabaseStart;
                        if (len == 0) {
                            // No database name
                            throw new ArgumentException();
                        }

                        database = outputCacheString.Substring(iDatabaseStart, len);
                        iTableStart = i+1;
                        continue;
                    }
                }

                return dependencies;

            }
            catch (ArgumentException) {
                throw new ArgumentException(SR.GetString(SR.Invalid_sqlDependency_argument, outputCacheString));
            }
        }
    }

    [Serializable()]
    public sealed class DatabaseNotEnabledForNotificationException : SystemException {

        public DatabaseNotEnabledForNotificationException() {
        }

        public DatabaseNotEnabledForNotificationException(String message)
        : base(message) {
        }

        public DatabaseNotEnabledForNotificationException(string message, Exception innerException)
        : base (message, innerException) {
        }

        internal DatabaseNotEnabledForNotificationException(SerializationInfo info, StreamingContext context)
        : base(info, context) {
        }

    }

    [Serializable()]
    public sealed class TableNotEnabledForNotificationException : SystemException {

        public TableNotEnabledForNotificationException() {
        }

        public TableNotEnabledForNotificationException(String message)
        : base(message) {
        }

        public TableNotEnabledForNotificationException(string message, Exception innerException)
        : base (message, innerException) {
        }

        internal TableNotEnabledForNotificationException(SerializationInfo info, StreamingContext context)
        : base(info, context) {
        }

    }

    // A class to store the state of a timer for a specific database
    internal class DatabaseNotifState : IDisposable {
        internal string         _database;
        internal string         _connectionString;
        internal int            _rqInCallback;
        internal bool           _notifEnabled;     // true means the ChangeNotif table was found in the database
        internal bool           _init;      // true means timer callback was called at least once
        internal Timer          _timer;
        internal Hashtable      _tables; // Names of all the tables registered for notification
        internal Exception      _pollExpt;
        internal int            _pollSqlError;
        internal SqlConnection  _sqlConn;
        internal SqlCommand     _sqlCmd;
        internal bool           _poolConn;
        internal DateTime       _utcTablesUpdated; // Time when _tables was last updated
        internal int            _refCount = 0;

        public void Dispose() {
            if (_sqlConn != null) {
                _sqlConn.Close();
                _sqlConn = null;
            }

            if (_timer != null) {
                _timer.Dispose();
                _timer = null;
            }
        }

        internal DatabaseNotifState(string database, string connection, int polltime) {
            _database = database;
            _connectionString = connection;
            _timer = null;
            _tables = new Hashtable();
            _pollExpt = null;
            _utcTablesUpdated = DateTime.MinValue;

            // We will pool the connection if the polltime is less than 5 s.
            if (polltime <= 5000) {
                _poolConn = true;
            }

        }

        internal void GetConnection(out SqlConnection sqlConn, out SqlCommand sqlCmd) {
            sqlConn = null;
            sqlCmd = null;

            // !!! Please note that GetConnection and ReleaseConnection does NOT support
            // multithreading.  The caller must do the locking.

            if (_sqlConn != null) {
                // We already have a pooled connection.
                Debug.Assert(_poolConn, "_poolConn");
                Debug.Assert(_sqlCmd != null, "_sqlCmd != null");

                sqlConn = _sqlConn;
                sqlCmd = _sqlCmd;

                _sqlConn = null;
                _sqlCmd = null;
            }
            else {
                SqlConnectionHolder holder = null;

                try {
                    holder = SqlConnectionHelper.GetConnection(_connectionString, true);

                    sqlCmd = new SqlCommand(SqlCacheDependencyManager.SQL_POLLING_SP_DBO, holder.Connection);

                    sqlConn = holder.Connection;
                }
                catch {
                    if (holder != null) {
                        holder.Close();
                        holder = null;
                    }

                    sqlCmd = null;

                    throw;
                }
            }
        }

        internal void ReleaseConnection(ref SqlConnection sqlConn, ref SqlCommand sqlCmd, bool error) {
            // !!! Please note that GetConnection and ReleaseConnection does NOT support
            // multithreading.  The caller must do the locking.

            if (sqlConn == null) {
                Debug.Assert(sqlCmd == null, "sqlCmd == null");
                return;
            }

            Debug.Assert(sqlCmd != null, "sqlCmd != null");

            if (_poolConn && !error) {
                _sqlConn = sqlConn;
                _sqlCmd = sqlCmd;
            }
            else {
                sqlConn.Close();
            }

            sqlConn = null;
            sqlCmd = null;
        }
    }

    internal static class SqlCacheDependencyManager{

        internal const bool     ENABLED_DEFAULT = true;
        internal const int      POLLTIME_DEFAULT = 60000;
        internal const int      TABLE_NAME_LENGTH = 128;

        internal const int      SQL_EXCEPTION_SP_NOT_FOUND = 2812;
        internal const int      SQL_EXCEPTION_PERMISSION_DENIED_ON_OBJECT = 229;
        internal const int      SQL_EXCEPTION_PERMISSION_DENIED_ON_DATABASE = 262;
        internal const int      SQL_EXCEPTION_PERMISSION_DENIED_ON_USER = 2760;
        internal const int      SQL_EXCEPTION_NO_GRANT_PERMISSION = 4613;
        internal const int      SQL_EXCEPTION_ADHOC = 50000;

        const char              CacheKeySeparatorChar = ':';
        const string            CacheKeySeparator = ":";
        const string            CacheKeySeparatorEscaped = "\\:";

        internal const string   SQL_CUSTOM_ERROR_TABLE_NOT_FOUND = "00000001";

        internal const string   SQL_NOTIF_TABLE =
                                "AspNet_SqlCacheTablesForChangeNotification";

        internal const string   SQL_POLLING_SP =
                                "AspNet_SqlCachePollingStoredProcedure";

        internal const string   SQL_POLLING_SP_DBO =
                                "dbo.AspNet_SqlCachePollingStoredProcedure";

        internal static TimeSpan    OneSec = new TimeSpan(0, 0, 1);

        internal static Hashtable   s_DatabaseNotifStates = new Hashtable();
        static TimerCallback        s_timerCallback = new TimerCallback(PollCallback);
        static int                  s_activePolling = 0;
        static bool                 s_shutdown = false;

        static internal string GetMoniterKey(string database, string table) {
            if (database.IndexOf(CacheKeySeparatorChar) != -1) {
                database = database.Replace(CacheKeySeparator, CacheKeySeparatorEscaped);
            }

            if (table.IndexOf(CacheKeySeparatorChar) != -1) {
                table = table.Replace(CacheKeySeparator, CacheKeySeparatorEscaped);
            }

            // If we don't escape our separator char (':') in database and table,
            // these two pairs of inputs will then generate the same key:
            // 1. database = "b", table = "b:b"
            // 2. database = "b:b", table = "b"
            return CacheInternal.PrefixSqlCacheDependency + database + CacheKeySeparator + table;
        }

        static internal void Dispose(int waitTimeoutMs) {
            try {
                DateTime waitLimit = DateTime.UtcNow.AddMilliseconds(waitTimeoutMs);

                Debug.Assert(s_shutdown != true, "s_shutdown != true");
                Debug.Trace("SqlCacheDependencyManager", "Dispose is called");

                s_shutdown = true;

                if (s_DatabaseNotifStates != null && s_DatabaseNotifStates.Count > 0) {
                    // Lock it because InitPolling could be modifying it.
                    lock(s_DatabaseNotifStates) {
                        foreach(DictionaryEntry entry in s_DatabaseNotifStates) {
                            object  obj = entry.Value;
                            if (obj != null) {
                                ((DatabaseNotifState)obj).Dispose();
                            }
                        }
                    }

                    for (;;) {
                        if (s_activePolling == 0)
                            break;

                        Thread.Sleep(250);

                        // only apply timeout if a managed debugger is not attached
                        if (!System.Diagnostics.Debugger.IsAttached && DateTime.UtcNow > waitLimit) {
                            break; // give it up
                        }
                    }
                }
            }
            catch {
                // It's called by HttpRuntime.Dispose. It can't throw anything.
                return;
            }
        }

        internal static SqlCacheDependencyDatabase GetDatabaseConfig(string database) {
            SqlCacheDependencySection config = RuntimeConfig.GetAppConfig().SqlCacheDependency;
            object  obj;

            obj =  config.Databases[database];
            if (obj == null) {
                throw new HttpException(SR.GetString(SR.Database_not_found, database));
            }

            return  (SqlCacheDependencyDatabase)obj;
        }

        // Initialize polling for a database.  It will:
        // 1. Create the DatabaseNotifState that holds the polling status about this database.
        // 2. Create the timer to poll.
        internal static void InitPolling(string database) {
            SqlCacheDependencySection config = RuntimeConfig.GetAppConfig().SqlCacheDependency;;
            SqlCacheDependencyDatabase  sqlDepDB;
            string connectionString;

            Debug.Trace("SqlCacheDependencyManager",
                                "InitPolling is called.  Database=" + database);

            // Return if polling isn't even enabled.
            if (!config.Enabled) {
                throw new ConfigurationErrorsException(
                    SR.GetString(SR.Polling_not_enabled_for_sql_cache),
                    config.ElementInformation.Properties["enabled"].Source, config.ElementInformation.Properties["enabled"].LineNumber);
            }

            // Return if the polltime is zero.  It means polling is disabled for this database.
            sqlDepDB = GetDatabaseConfig(database);
            if (sqlDepDB.PollTime == 0) {
                throw new ConfigurationErrorsException(
                    SR.GetString(SR.Polltime_zero_for_database_sql_cache, database),
                    sqlDepDB.ElementInformation.Properties["pollTime"].Source, sqlDepDB.ElementInformation.Properties["pollTime"].LineNumber);
            }

            if (s_DatabaseNotifStates.ContainsKey(database)) {
                // Someone has already started the timer for this database.
                Debug.Trace("SqlCacheDependencyManager",
                                "InitPolling: Timer already started for " + database);

                return;
            }

            connectionString = SqlConnectionHelper.GetConnectionString(sqlDepDB.ConnectionStringName, true, true);
            if (connectionString == null || connectionString.Length < 1) {
                throw new ConfigurationErrorsException(
                    SR.GetString(SR.Connection_string_not_found, sqlDepDB.ConnectionStringName),
                    sqlDepDB.ElementInformation.Properties["connectionStringName"].Source, sqlDepDB.ElementInformation.Properties["connectionStringName"].LineNumber);
            }

            lock(s_DatabaseNotifStates) {
                DatabaseNotifState   state;

                if (s_DatabaseNotifStates.ContainsKey(database)) {
                    // Someone has already started the timer for this database.
                    Debug.Trace("SqlCacheDependencyManager",
                                "InitPolling: Timer already started for " + database);

                    return;
                }

                Debug.Trace("SqlCacheDependencyManager",
                                "InitPolling: Creating timer for " + database);

                state = new DatabaseNotifState(database, connectionString, sqlDepDB.PollTime);
                state._timer = new Timer(s_timerCallback, state, 0 /* dueTime */, sqlDepDB.PollTime /* period */);

                s_DatabaseNotifStates.Add(database, state);
            }
        }

        // Timer callback function.
        static void PollCallback(object state) {
            using (new ApplicationImpersonationContext()) {
                PollDatabaseForChanges((DatabaseNotifState)state, true /*fromTimer*/);
            }
        }

        // Query all the entries from the AspNet_SqlCacheTablesForChangeNotification
        // table and update the values in the cache accordingly.
        //
        // This is mainly called by the timer callback.  But will also be called by
        // UpdateDatabaseNotifState, which polls for changes on demand.
        internal static void PollDatabaseForChanges(DatabaseNotifState dbState, bool fromTimer) {
            SqlDataReader       sqlReader = null;
            SqlConnection       sqlConn = null;
            SqlCommand          sqlCmd = null;
            int                 changeId;
            string              tableName;
            CacheInternal       cacheInternal = HttpRuntime.CacheInternal;
            string              monitorKey;
            object              obj;
            bool                notifEnabled = false;
            Exception           pollExpt = null;
            SqlException        sqlExpt = null;

            Debug.Trace("SqlCacheDependencyManagerPolling",
                "PollCallback called; connection=" + dbState._connectionString);

            if (s_shutdown) {
                return;
            }

            // If this call is from a timer, and if the refcount for this database is zero,
            // we will ignore it. The exception is if dbState._init == false,
            // which means the timer is polling it for the first time.
            if (dbState._refCount == 0 && fromTimer && dbState._init  ) {
                Debug.Trace("SqlCacheDependencyManagerPolling",
                    "PollCallback ignored for " + dbState._database + " because refcount is 0");
                return;
            }

            // Grab the lock, which allows only one thread to enter this method.
            if (Interlocked.CompareExchange(ref dbState._rqInCallback, 1, 0) != 0) {

                // We can't get the lock.

                if (!fromTimer) {
                    // A non-timer caller will really want to make a call to SQL and
                    // get the result.  So if another thread is calling this, we'll
                    // wait for it to be done.
                    int         timeout;
                    HttpContext context = HttpContext.Current;

                    if (context == null) {
                        timeout = 30;
                    }
                    else {
                        timeout = Math.Max(context.Timeout.Seconds / 3, 30);
                    }
                    DateTime waitLimit = DateTime.UtcNow.Add(new TimeSpan(0, 0, timeout));

                    for (;;) {
                        if (Interlocked.CompareExchange(ref dbState._rqInCallback, 1, 0) == 0) {
                            break;
                        }

                        Thread.Sleep(250);

                        if (s_shutdown) {
                            return;
                        }

                        // only apply timeout if a managed debugger is not attached
                        if (!System.Diagnostics.Debugger.IsAttached && DateTime.UtcNow > waitLimit) {
                            // We've waited and retried for 5 seconds.
                            // Somehow PollCallback haven't finished its first call for this database
                            // Assume we cannot connect to SQL.
                            throw new HttpException(
                                SR.GetString(SR.Cant_connect_sql_cache_dep_database_polling, dbState._database));
                        }
                    }
                }
                else {
                    // For a timer callback, if another thread is updating the data for
                    // this database, this thread will just leave and let that thread
                    // finish the update job.
                    Debug.Trace("SqlCacheDependencyManagerPolling",
                        "PollCallback returned because another thread is updating the data");
                    return;
                }
            }

            try {
                try {
                    // Keep a count on how many threads are polling right now
                    // This counter is used by Dispose()
                    Interlocked.Increment(ref s_activePolling);

                    // The below assert was commented out because this method is either
                    // called by a timer thread, or thru the SqlCacheDependencyAdmin APIs.
                    // In the latter case, the caller should have the permissions.
                    //(new SqlClientPermission(PermissionState.Unrestricted)).Assert();

                    dbState.GetConnection(out sqlConn, out sqlCmd);
                    sqlReader = sqlCmd.ExecuteReader();

                    // If we got stuck for a long time in the ExecuteReader above,
                    // Dispose() may have given up already while waiting for this thread to finish
                    if (s_shutdown) {
                        return;
                    }

                    // ExecuteReader() succeeded, and that means we at least have found the notification table.
                    notifEnabled = true;

                    // Remember the original list of tables that are enabled
                    Hashtable   originalTables = (Hashtable)dbState._tables.Clone();

                    while(sqlReader.Read()) {
                        tableName = sqlReader.GetString(0);
                        changeId = sqlReader.GetInt32(1);

                        Debug.Trace("SqlCacheDependencyManagerPolling",
                                "Database=" + dbState._database+ "; tableName=" + tableName + "; changeId=" + changeId);

                        monitorKey = GetMoniterKey(dbState._database, tableName);
                        obj = cacheInternal[monitorKey];

                        if (obj == null) {
                            Debug.Assert(!dbState._tables.ContainsKey(tableName),
                                        "DatabaseNotifStae._tables and internal cache keys should be in-[....]");

                            Debug.Trace("SqlCacheDependencyManagerPolling",
                                "Add Database=" + dbState._database+ "; tableName=" + tableName + "; changeId=" + changeId);

                            cacheInternal.UtcAdd(monitorKey, changeId, null,
                                        Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration,
                                        CacheItemPriority.NotRemovable, null);

                            dbState._tables.Add(tableName, null);
                        }
                        else if (changeId != (int)obj) {
                            Debug.Assert(dbState._tables.ContainsKey(tableName),
                                        "DatabaseNotifStae._tables and internal cache keys should be in-[....]");

                            Debug.Trace("SqlCacheDependencyManagerPolling",
                                    "Change Database=" + dbState._database+ "; tableName=" + tableName + "; old=" + (int)obj + "; new=" + changeId);

                            // ChangeId is different. It means some table changes have happened.
                            // Update local cache value
                            cacheInternal.UtcInsert(monitorKey, changeId, null,
                                        Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration,
                                        CacheItemPriority.NotRemovable, null);
                        }

                        originalTables.Remove(tableName);
                    }

                    // What's left in originalTables are the ones that're no longer
                    // contained in the AspNet_SqlCacheTablesForChangeNotification
                    // table in the database.

                    // Remove tables which are no longer enabled for notification
                    foreach(object key in originalTables.Keys) {
                        dbState._tables.Remove((string)key);
                        cacheInternal.Remove(GetMoniterKey(dbState._database, (string)key));

                        Debug.Trace("SqlCacheDependencyManagerPolling",
                                "Remove Database=" + dbState._database+ "; key=" + key);
                    }

                    // Clear old error, if any.
                    if (dbState._pollSqlError != 0) {
                        dbState._pollSqlError = 0;
                    }
                }
                catch (Exception e) {
                    pollExpt = e;

                    sqlExpt = e as SqlException;
                    if (sqlExpt != null) {
                        Debug.Trace("SqlCacheDependencyManagerPolling", "Error reading rows.  SqlException:"+
                            "\nMessage=" + sqlExpt.Message +
                            "\nNumber=" + sqlExpt.Number);

                        dbState._pollSqlError = sqlExpt.Number;
                    }
                    else {
                        dbState._pollSqlError = 0;
                        Debug.Trace("SqlCacheDependencyManagerPolling", "Error reading rows.  Exception:"+ pollExpt);
                    }
                }
                finally {
                    try {
                        if (sqlReader != null) {
                            sqlReader.Close();
                        }

                        dbState.ReleaseConnection(ref sqlConn, ref sqlCmd, pollExpt != null);
                    }
                    catch {
                    }

                    // Need locking because EnsureTableIsRegisteredAndPolled() assumes
                    // the fields in a dbState are set atomically.
                    lock(dbState) {
                        dbState._pollExpt = pollExpt;

                        // If we have changed from being enabled to disabled, and
                        // it's because we cannot find the SP for polling, it means
                        // the database is no longer enabled for sql cache dependency.
                        // we should invalidate all cache items depending on any
                        // table on this database
                        if (dbState._notifEnabled && !notifEnabled &&
                            pollExpt != null && dbState._pollSqlError == SQL_EXCEPTION_SP_NOT_FOUND) {
                            foreach(object key in dbState._tables.Keys) {
                                try {
                                    cacheInternal.Remove(GetMoniterKey(dbState._database, (string)key));
                                }
                                catch {}

                                Debug.Trace("SqlCacheDependencyManagerPolling",
                                    "Changed to disabled.  Remove Database=" + dbState._database+ "; key=" + key);
                            }

                            // Since we have removed all the cache items related to this database,
                            // the _refCount of this database will drop to zero, and thus the timer
                            // callback will not poll this database.
                            // So we have to cleanup _tables now.
                            dbState._tables.Clear();
                        }

                        dbState._notifEnabled = notifEnabled;
                        dbState._utcTablesUpdated = DateTime.UtcNow;

                        Debug.Trace("SqlCacheDependencyManagerPolling", "dbState:_pollExpt="+ dbState._pollExpt +
                                "; _pollSqlError=" + dbState._pollSqlError + "; _notifEnabled=" + dbState._notifEnabled +
                                "; __utcTablesUpdated=" + dbState._utcTablesUpdated);
                    }

                    // Mark dbState as initialized by PollCallback for the first time.
                    // EnsureTableIsRegisteredAndPolled() depends on this.
                    if (dbState._init != true) {
                        dbState._init = true;
                    }

                    Interlocked.Decrement(ref s_activePolling);

                    // Release the lock
                    Interlocked.Exchange(ref dbState._rqInCallback, 0);
                }
            }
            catch { throw; }    // Prevent Exception Filter Security Issue (ASURT 122835)
        }

        // Called by SqlCacheDependency.GetDependKey
        static internal void EnsureTableIsRegisteredAndPolled(string database, string table) {
            bool    doubleChecked = false;

            // First check.  If the cache key exists, that means the first poll request
            // for this table has successfully completed
            Debug.Trace("SqlCacheDependencyManagerCheck",
                                "Check is called.  Database=" + database+ "; table=" + table);

            if (HttpRuntime.CacheInternal[GetMoniterKey(database, table)] != null) {
                return;
            }

            // Initilize polling for this database, if needed.
            InitPolling(database);

            // Wait until this database is initialized by PollCallback for the first time
            DatabaseNotifState  dbState = (DatabaseNotifState)s_DatabaseNotifStates[database];

            if (!dbState._init) {
                int         timeout;
                HttpContext context = HttpContext.Current;

                if (context == null) {
                    timeout = 30;
                }
                else {
                    timeout = Math.Max(context.Timeout.Seconds / 3, 30);
                }
                DateTime waitLimit = DateTime.UtcNow.Add(new TimeSpan(0, 0, timeout));

                Debug.Trace("SqlCacheDependencyManagerCheck", "Waiting for intialization: timeout=" + timeout + "s");

                for (;;) {
                    if (dbState._init)
                        break;

                    Thread.Sleep(250);

                    // only apply timeout if a managed debugger is not attached
                    if (!System.Diagnostics.Debugger.IsAttached && DateTime.UtcNow > waitLimit) {
                        // We've waited and retried for waitLimit amount of time.
                        // Still PollCallback haven't finished its first call for this database
                        // Assume we cannot connect to SQL.
                        throw new HttpException(
                            SR.GetString(SR.Cant_connect_sql_cache_dep_database_polling, database));
                    }
                }
            }

            while(true) {
                DateTime    utcTablesLastUpdated;
                bool        dbRegistered;
                Exception   pollException;
                int         pollSqlError = 0;

                lock(dbState) {
                     Debug.Trace("SqlCacheDependencyManagerCheck", "dbState:_pollExpt="+ dbState._pollExpt +
                                "; _pollSqlError=" + dbState._pollSqlError + "; _notifEnabled=" + dbState._notifEnabled );

                    pollException = dbState._pollExpt;
                    if (pollException != null) {
                        pollSqlError = dbState._pollSqlError;
                    }

                    utcTablesLastUpdated = dbState._utcTablesUpdated;
                    dbRegistered = dbState._notifEnabled;
                }

                if (pollException == null &&    // No exception from polling
                    dbRegistered &&             // The database is registered
                    dbState._tables.ContainsKey(table)) {   // The table is also registered
                    Debug.Trace("SqlCacheDependencyManagerCheck", "The table is registered too.  Exit now!");
                    return;
                }

                // Either we hit an error in the last polling, or the database or the table
                // isn't registered.
                //
                // See if we can double check.  Double checking is needed because the
                // results we just looked at might be collected only at last poll time,
                // which could be quite old, depending on the pollTime setting.
                //
                // The scenario we try to solve is:
                // 1. Let's say polling is configured to happen every 1 minute, and we just poll.
                // 2. A page then registers a table for notification.
                // 3. The page then try to use SqlCacheDependency on that table.
                // 4. If we don't call UpdateDatabaseNotifStat to query the database now,
                //    we'll have to wait for a whole minute before we can use that table.
                //

                // To prevent the SQL server from being bombarded by this kind of per-client-request
                // adhoc check, we only allow a max of one double check per second per database
                if (!doubleChecked &&
                    DateTime.UtcNow - utcTablesLastUpdated >= OneSec) {

                    Debug.Trace("SqlCacheDependencyManagerCheck", "Double check...");
                    UpdateDatabaseNotifState(database);
                    doubleChecked = true;
                    continue;
                }

                if (pollSqlError == SQL_EXCEPTION_SP_NOT_FOUND) {
                    // This error happens if the database isn't enabled for notification.
                    // This doesn't count as a real Sql error
                    Debug.Assert(dbRegistered == false, "When this error happened, we shouldn't be able to poll the database");
                    pollException = null;
                }

                // Report any error if we failed in the last PollCallback
                if (pollException != null) {
                    string  error;

                    if (pollSqlError == SQL_EXCEPTION_PERMISSION_DENIED_ON_OBJECT ||
                        pollSqlError == SQL_EXCEPTION_PERMISSION_DENIED_ON_DATABASE) {
                        error = SR.Permission_denied_database_polling;
                    }
                    else {
                        error = SR.Cant_connect_sql_cache_dep_database_polling;
                    }

                    HttpException outerException = new HttpException(
                           SR.GetString(error, database), pollException);

                    outerException.SetFormatter(new UseLastUnhandledErrorFormatter(outerException));

                    throw outerException;
                }

                // If we don't get any error, then either the database or the table isn't registered.
                if (dbRegistered == false) {
                    throw new DatabaseNotEnabledForNotificationException(
                            SR.GetString(SR.Database_not_enabled_for_notification, database));
                }
                else {
                    throw new TableNotEnabledForNotificationException(
                            SR.GetString(SR.Table_not_enabled_for_notification, table, database));
                }
            }
        }

        // Do a on-demand polling of the database in order to obtain the latest
        // data.
        internal static void UpdateDatabaseNotifState(string database) {
            using (new ApplicationImpersonationContext()) {
                Debug.Trace("SqlCacheDependencyManager", "UpdateDatabaseNotifState called for database " + database +
                    "; running as " + WindowsIdentity.GetCurrent().Name);

                // Make sure we have initialized the polling of this database
                InitPolling(database);
                Debug.Assert(s_DatabaseNotifStates[database] != null, "s_DatabaseNotifStates[database] != null");

                PollDatabaseForChanges((DatabaseNotifState)s_DatabaseNotifStates[database], false /*fromTimer*/);
            }
        }

        // Update all initialized databases
        internal static void UpdateAllDatabaseNotifState() {
            lock(s_DatabaseNotifStates) {
                foreach(DictionaryEntry entry in s_DatabaseNotifStates) {
                    DatabaseNotifState  state = (DatabaseNotifState)entry.Value;
                    if (state._init) {
                        UpdateDatabaseNotifState((string)entry.Key);
                    }
                }
            }
        }

        internal static DatabaseNotifState AddRef(string database) {
            DatabaseNotifState dbState = (DatabaseNotifState)s_DatabaseNotifStates[database];
            Debug.Assert(dbState != null, "AddRef: s_DatabaseNotifStates[database] != null");

#if DBG
            int res =
#endif
            Interlocked.Increment(ref dbState._refCount);
#if DBG
            Debug.Trace("SqlCacheDependencyManager", "AddRef called for " + database + "; res=" + res);
            Debug.Assert(res > 0, "AddRef result for " + database + " must be > 0");
#endif
            return dbState;
        }

        internal static void Release(DatabaseNotifState dbState) {
#if DBG
            int res =
#endif
            Interlocked.Decrement(ref dbState._refCount);
#if DBG
            Debug.Trace("SqlCacheDependencyManager", "Release called for " + dbState._database + "; res=" + res);
            Debug.Assert(res >= 0, "Release result for " + dbState._database + " must be >= 0");
#endif
        }
    }

    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.High)]
    public static class SqlCacheDependencyAdmin {

        // Note:
        // In all the SQL statements below, we will do an unlocking
        // SELECT, followed by a locking SELECT.  This is to avoid
        // duplication operation.

        //
        // {0} = SQL_NOTIF_TABLE
        // {1} = SQL_POLLING_SP
        // {2} = SQL_REGISTER_TABLE_SP
        // {3} = SQL_TRIGGER_NAME_POSTFIX
        // {4} = SQL_UNREGISTER_TABLE_SP
        // {5} = SQL_QUERY_REGISTERED_TABLES_SP
        // {6} = SQL_UPDATE_CHANGE_ID_SP
        //
        internal const string   SQL_CREATE_ENABLE_DATABASE_SP =
        "/* Create notification table */ \n" +
        "IF NOT EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{0}' AND type = 'U') \n" +
        "   IF NOT EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{0}' AND type = 'U') \n" +
        "      CREATE TABLE dbo.{0} (\n" +
        "      tableName             NVARCHAR(450) NOT NULL PRIMARY KEY,\n" +
        "      notificationCreated   DATETIME NOT NULL DEFAULT(GETDATE()),\n" +
        "      changeId              INT NOT NULL DEFAULT(0)\n" +
        "      )\n" +
        "\n" +
        "/* Create polling SP */\n" +
        "IF NOT EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{1}' AND type = 'P') \n" +
        "   IF NOT EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{1}' AND type = 'P') \n" +
        "   EXEC('CREATE PROCEDURE dbo.{1} AS\n" +
        "         SELECT tableName, changeId FROM dbo.{0}\n" +
        "         RETURN 0')\n" +
        "\n" +
        "/* Create SP for registering a table. */ \n" +
        "IF NOT EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{2}' AND type = 'P') \n" +
        "   IF NOT EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{2}' AND type = 'P') \n" +
        "   EXEC('CREATE PROCEDURE dbo.{2} \n" +
        "             @tableName NVARCHAR(450) \n" +
        "         AS\n" +
        "         BEGIN\n" +
        "\n" +
        "         DECLARE @triggerName AS NVARCHAR(3000) \n" +
        "         DECLARE @fullTriggerName AS NVARCHAR(3000)\n" +
        "         DECLARE @canonTableName NVARCHAR(3000) \n" +
        "         DECLARE @quotedTableName NVARCHAR(3000) \n" +
        "\n" +
        "         /* Create the trigger name */ \n" +
        "         SET @triggerName = REPLACE(@tableName, ''['', ''__o__'') \n" +
        "         SET @triggerName = REPLACE(@triggerName, '']'', ''__c__'') \n" +
        "         SET @triggerName = @triggerName + ''{3}'' \n" +
        "         SET @fullTriggerName = ''dbo.['' + @triggerName + '']'' \n" +
        "\n" +
        "         /* Create the cannonicalized table name for trigger creation */ \n" +
        "         /* Do not touch it if the name contains other delimiters */ \n" +
        "         IF (CHARINDEX(''.'', @tableName) <> 0 OR \n" +
        "             CHARINDEX(''['', @tableName) <> 0 OR \n" +
        "             CHARINDEX('']'', @tableName) <> 0) \n" +
        "             SET @canonTableName = @tableName \n" +
        "         ELSE \n" +
        "             SET @canonTableName = ''['' + @tableName + '']'' \n" +
        "\n" +
        "         /* First make sure the table exists */ \n" +
        "         IF (SELECT OBJECT_ID(@tableName, ''U'')) IS NULL \n" +
        "         BEGIN \n" +
        "             RAISERROR (''" + SqlCacheDependencyManager.SQL_CUSTOM_ERROR_TABLE_NOT_FOUND + "'', 16, 1) \n" +
        "             RETURN \n" +
        "         END \n" +
        "\n" +
        "         BEGIN TRAN\n" +
        "         /* Insert the value into the notification table */ \n" +
        "         IF NOT EXISTS (SELECT tableName FROM dbo.{0} WITH (NOLOCK) WHERE tableName = @tableName) \n" +
        "             IF NOT EXISTS (SELECT tableName FROM dbo.{0} WITH (TABLOCKX) WHERE tableName = @tableName) \n" +
        "                 INSERT  dbo.{0} \n" +
        "                 VALUES (@tableName, GETDATE(), 0)\n" +
        "\n" +
        "         /* Create the trigger */ \n" +
        "         SET @quotedTableName = QUOTENAME(@tableName, '''''''') \n" +
        "         IF NOT EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = @triggerName AND type = ''TR'') \n" +
        "             IF NOT EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = @triggerName AND type = ''TR'') \n" +
        "                 EXEC(''CREATE TRIGGER '' + @fullTriggerName + '' ON '' + @canonTableName +''\n" +
        "                       FOR INSERT, UPDATE, DELETE AS BEGIN\n" +
        "                       SET NOCOUNT ON\n" +
        "                       EXEC dbo.{6} N'' + @quotedTableName + ''\n" +
        "                       END\n" +
        "                       '')\n" +
        "         COMMIT TRAN\n" +
        "         END\n" +
        "   ')\n" +
        "\n" +
        "/* Create SP for updating the change Id of a table. */ \n" +
        "IF NOT EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{6}' AND type = 'P') \n" +
        "   IF NOT EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{6}' AND type = 'P') \n" +
        "   EXEC('CREATE PROCEDURE dbo.{6} \n" +
        "             @tableName NVARCHAR(450) \n" +
        "         AS\n" +
        "\n" +
        "         BEGIN \n" +
        "             UPDATE dbo.{0} WITH (ROWLOCK) SET changeId = changeId + 1 \n" +
        "             WHERE tableName = @tableName\n" +
        "         END\n" +
        "   ')\n" +
        "\n" +
        "/* Create SP for unregistering a table. */ \n" +
        "IF NOT EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{4}' AND type = 'P') \n" +
        "   IF NOT EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{4}' AND type = 'P') \n" +
        "   EXEC('CREATE PROCEDURE dbo.{4} \n" +
        "             @tableName NVARCHAR(450) \n" +
        "         AS\n" +
        "         BEGIN\n" +
        "\n" +
        "         BEGIN TRAN\n" +
        "         DECLARE @triggerName AS NVARCHAR(3000) \n" +
        "         DECLARE @fullTriggerName AS NVARCHAR(3000)\n" +
        "         SET @triggerName = REPLACE(@tableName, ''['', ''__o__'') \n" +
        "         SET @triggerName = REPLACE(@triggerName, '']'', ''__c__'') \n" +
        "         SET @triggerName = @triggerName + ''{3}'' \n" +
        "         SET @fullTriggerName = ''dbo.['' + @triggerName + '']'' \n" +
        "\n" +
        "         /* Remove the table-row from the notification table */ \n" +
        "         IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = ''{0}'' AND type = ''U'') \n" +
        "             IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = ''{0}'' AND type = ''U'') \n" +
        "             DELETE FROM dbo.{0} WHERE tableName = @tableName \n" +
        "\n" +
        "         /* Remove the trigger */ \n" +
        "         IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = @triggerName AND type = ''TR'') \n" +
        "             IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = @triggerName AND type = ''TR'') \n" +
        "             EXEC(''DROP TRIGGER '' + @fullTriggerName) \n" +
        "\n" +
        "         COMMIT TRAN\n" +
        "         END\n" +
        "   ')\n" +
        "\n" +
        "/* Create SP for querying all registered table */ \n" +
        "IF NOT EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{5}' AND type = 'P') \n" +
        "   IF NOT EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{5}' AND type = 'P') \n" +
        "   EXEC('CREATE PROCEDURE dbo.{5} \n" +
        "         AS\n" +
        "         SELECT tableName FROM dbo.{0}" +
        "   ')\n" +
        "\n" +
        "/* Create roles and grant them access to SP  */ \n" +
        "IF NOT EXISTS (SELECT name FROM sysusers WHERE issqlrole = 1 AND name = N'aspnet_ChangeNotification_ReceiveNotificationsOnlyAccess') \n" +
        "    EXEC sp_addrole N'aspnet_ChangeNotification_ReceiveNotificationsOnlyAccess' \n" +
        "\n" +
        "GRANT EXECUTE ON dbo.{1} to aspnet_ChangeNotification_ReceiveNotificationsOnlyAccess\n" +
        "\n";

        //
        // {0} = SQL_NOTIF_TABLE
        // {1} = SQL_POLLING_SP
        // {2} = SQL_REGISTER_TABLE_SP
        // {3} = SQL_UNREGISTER_TABLE_SP
        // {4} = SQL_QUERY_REGISTERED_TABLES_SP
        // {5} = SQL_UPDATE_CHANGE_ID_SP
        //
        internal const string   SQL_DISABLE_DATABASE =
        "/* Remove notification table */ \n" +
        "IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{0}' AND type = 'U') \n" +
        "    IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{0}' AND type = 'U') \n" +
        "    BEGIN\n" +
        "      /* First, unregister all registered tables */ \n" +
        "      DECLARE tables_cursor CURSOR FOR \n" +
        "      SELECT tableName FROM dbo.{0} \n" +
        "      DECLARE @tableName AS NVARCHAR(450) \n" +
        "\n" +
        "      OPEN tables_cursor \n" +
        "\n" +
        "      /* Perform the first fetch. */ \n" +
        "      FETCH NEXT FROM tables_cursor INTO @tableName \n" +
        "\n" +
        "      /* Check @@FETCH_STATUS to see if there are any more rows to fetch. */ \n" +
        "      WHILE @@FETCH_STATUS = 0 \n" +
        "      BEGIN \n" +
        "          EXEC {3} @tableName \n" +
        "\n" +
        "          /* This is executed as long as the previous fetch succeeds. */ \n" +
        "          FETCH NEXT FROM tables_cursor INTO @tableName \n" +
        "      END \n" +
        "      CLOSE tables_cursor \n" +
        "      DEALLOCATE tables_cursor \n" +
        "\n" +
        "      /* Drop the table */\n" +
        "      DROP TABLE dbo.{0} \n" +
        "    END\n" +
        "\n" +
        "/* Remove polling SP */ \n" +
        "IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{1}' AND type = 'P') \n" +
        "    IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{1}' AND type = 'P') \n" +
        "      DROP PROCEDURE dbo.{1} \n" +
        "\n" +
        "/* Remove SP that registers a table */ \n" +
        "IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{2}' AND type = 'P') \n" +
        "    IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{2}' AND type = 'P') \n" +
        "      DROP PROCEDURE dbo.{2} \n" +
        "\n" +
        "/* Remove SP that unregisters a table */ \n" +
        "IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{3}' AND type = 'P') \n" +
        "    IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{3}' AND type = 'P') \n" +
        "      DROP PROCEDURE dbo.{3} \n"+
        "\n" +
        "/* Remove SP that querys the registered table */ \n" +
        "IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{4}' AND type = 'P') \n" +
        "    IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{4}' AND type = 'P') \n" +
        "      DROP PROCEDURE dbo.{4} \n" +
        "\n" +
        "/* Remove SP that updates the change Id of a table. */ \n" +
        "IF EXISTS (SELECT name FROM sysobjects WITH (NOLOCK) WHERE name = '{5}' AND type = 'P') \n" +
        "    IF EXISTS (SELECT name FROM sysobjects WITH (TABLOCKX) WHERE name = '{5}' AND type = 'P') \n" +
        "      DROP PROCEDURE dbo.{5} \n" +
        "\n" +
        "/* Drop roles */ \n" +
        "IF EXISTS ( SELECT name FROM sysusers WHERE issqlrole = 1 AND name = 'aspnet_ChangeNotification_ReceiveNotificationsOnlyAccess') BEGIN\n" +
        DROP_MEMBERS +
        "    EXEC sp_droprole 'aspnet_ChangeNotification_ReceiveNotificationsOnlyAccess'\n" +
        "END\n";

        internal const string   DROP_MEMBERS =
        "CREATE TABLE #aspnet_RoleMembers \n" +
        "( \n" +
        "    Group_name      sysname, \n" +
        "    Group_id        smallint, \n" +
        "    Users_in_group  sysname, \n" +
        "    User_id         smallint \n" +
        ") \n" +
        "INSERT INTO #aspnet_RoleMembers \n" +
        "EXEC sp_helpuser 'aspnet_ChangeNotification_ReceiveNotificationsOnlyAccess' \n" +
        " \n" +
        "DECLARE @user_id smallint \n" +
        "DECLARE @cmd nvarchar(500) \n" +
        "DECLARE c1 CURSOR FORWARD_ONLY FOR  \n" +
        "    SELECT User_id FROM #aspnet_RoleMembers \n" +
        "  \n" +
        "OPEN c1 \n" +
        "  \n" +
        "FETCH c1 INTO @user_id \n" +
        "WHILE (@@fetch_status = 0)  \n" +
        "BEGIN \n" +
        "    SET @cmd = 'EXEC sp_droprolemember ''aspnet_ChangeNotification_ReceiveNotificationsOnlyAccess'',''' + USER_NAME(@user_id) + '''' \n" +
        "    EXEC (@cmd) \n" +
        "    FETCH c1 INTO @user_id \n" +
        "END \n" +
        " \n" +
        "close c1 \n" +
        "deallocate c1 \n";

        internal const string   SQL_REGISTER_TABLE_SP =
                                "AspNet_SqlCacheRegisterTableStoredProcedure";

        internal const string   SQL_REGISTER_TABLE_SP_DBO =
                                "dbo.AspNet_SqlCacheRegisterTableStoredProcedure";

        internal const string   SQL_UNREGISTER_TABLE_SP =
                                "AspNet_SqlCacheUnRegisterTableStoredProcedure";

        internal const string   SQL_UNREGISTER_TABLE_SP_DBO =
                                "dbo.AspNet_SqlCacheUnRegisterTableStoredProcedure";

        internal const string   SQL_TRIGGER_NAME_POSTFIX =
                                "_AspNet_SqlCacheNotification_Trigger";

        internal const string   SQL_QUERY_REGISTERED_TABLES_SP =
                                "AspNet_SqlCacheQueryRegisteredTablesStoredProcedure";

        internal const string   SQL_QUERY_REGISTERED_TABLES_SP_DBO =
                                "dbo.AspNet_SqlCacheQueryRegisteredTablesStoredProcedure";

        internal const string   SQL_UPDATE_CHANGE_ID_SP=
                                "AspNet_SqlCacheUpdateChangeIdStoredProcedure";

        const int   SETUP_TABLE =           0x00000001;
        const int   SETUP_DISABLE =         0x00000002;
        const int   SETUP_HTTPREQUEST =     0x00000004;
        const int   SETUP_TABLES =          0x00000008; // We're called in a loop to setup an array of tables.

        internal static void SetupNotifications(int flags, string table, string connectionString) {
            SqlConnection   sqlConnection = null;
            SqlCommand      sqlCmd = null;
            bool            tableOp = (flags & (SETUP_TABLES|SETUP_TABLE)) != 0;
            bool            disable = (flags & SETUP_DISABLE) != 0;

            if (tableOp) {
                bool    tables = (flags & SETUP_TABLES) != 0;
                if (table == null) {
                    if (tables) {
                        throw new ArgumentException(SR.GetString(SR.Cache_null_table_in_tables),
                                            "tables");
                    }
                    else {
                        throw new ArgumentNullException("table");
                    }
                }
                else if (table.Length == 0) {
                    if (tables) {
                        throw new ArgumentException(SR.GetString(SR.Cache_null_table_in_tables),
                                    "tables");
                    }
                    else {
                        throw new ArgumentException(SR.GetString(SR.Cache_null_table),
                                    "table");
                    }
                }
            }

            try {
                sqlConnection = new SqlConnection(connectionString);
                sqlConnection.Open();

                sqlCmd = new SqlCommand(null, sqlConnection);

                if (tableOp) {
                    sqlCmd.CommandText = !disable ? SQL_REGISTER_TABLE_SP_DBO : SQL_UNREGISTER_TABLE_SP_DBO;
                    sqlCmd.CommandType = CommandType.StoredProcedure;
                    sqlCmd.Parameters.Add(new SqlParameter("@tableName", SqlDbType.NVarChar, table.Length));
                    sqlCmd.Parameters[0].Value = table;
                }
                else {
                    if (!disable) {
                        // Enable the database
                        sqlCmd.CommandText = String.Format(CultureInfo.InvariantCulture,
                                                SQL_CREATE_ENABLE_DATABASE_SP,
                                                SqlCacheDependencyManager.SQL_NOTIF_TABLE,
                                                SqlCacheDependencyManager.SQL_POLLING_SP,
                                                SQL_REGISTER_TABLE_SP,
                                                SQL_TRIGGER_NAME_POSTFIX,
                                                SQL_UNREGISTER_TABLE_SP,
                                                SQL_QUERY_REGISTERED_TABLES_SP,
                                                SQL_UPDATE_CHANGE_ID_SP);
                        sqlCmd.CommandType = CommandType.Text;
                    }
                    else {
                        // Disable the database
                        sqlCmd.CommandText = String.Format(CultureInfo.InvariantCulture,
                                                SQL_DISABLE_DATABASE,
                                                SqlCacheDependencyManager.SQL_NOTIF_TABLE,
                                                SqlCacheDependencyManager.SQL_POLLING_SP,
                                                SQL_REGISTER_TABLE_SP,
                                                SQL_UNREGISTER_TABLE_SP,
                                                SQL_QUERY_REGISTERED_TABLES_SP,
                                                SQL_UPDATE_CHANGE_ID_SP);
                        sqlCmd.CommandType = CommandType.Text;
                    }
                }

                Debug.Trace("SqlCacheDependencyAdmin", "\n" +
                    sqlCmd.CommandText);

                sqlCmd.ExecuteNonQuery();

                // Clear CommandText so that error handling won't mistakenly
                // report it as a SQL error
                sqlCmd.CommandText = String.Empty;

                // If we are being called as part of an ASP.NET Http request
                if (HttpRuntime.IsAspNetAppDomain) {
                    // Need to update the status of all initialized databases
                    //
                    // Note: we can actually try to figure out which database we want
                    // to update based on the connectionString.  But updating
                    // all initialized ones are good enough.
                    SqlCacheDependencyManager.UpdateAllDatabaseNotifState();
                }
            }
            catch (Exception e) {
                SqlException sqlExpt = e as SqlException;
                bool throwError = true;

                if (sqlExpt != null) {
                    Debug.Trace("SqlCacheDependencyAdmin", "SqlException:"+
                        "\nMessage=" + sqlExpt.Message +
                        "\nNumber=" + sqlExpt.Number);

                    if (sqlExpt.Number == SqlCacheDependencyManager.SQL_EXCEPTION_SP_NOT_FOUND) {
                        if (!disable) {
                            if (table != null) {
                                throw new DatabaseNotEnabledForNotificationException(
                                    SR.GetString(SR.Database_not_enabled_for_notification,
                                                                    sqlConnection.Database));
                            }
                            else {
                                throw;
                            }
                        }
                        else {
                            if (table != null) {
                                throw new DatabaseNotEnabledForNotificationException(
                                    SR.GetString(SR.Cant_disable_table_sql_cache_dep));
                            }
                            else {
                                // If we cannot find the SP for disabling the database, it maybe because
                                // SQL cache dep is already disabled, or the SP is missing.
                                // In either case, we just exit silently.
                                throwError = false;
                            }
                        }
                    }
                    else if (sqlExpt.Number == SqlCacheDependencyManager.SQL_EXCEPTION_PERMISSION_DENIED_ON_OBJECT ||
                            sqlExpt.Number == SqlCacheDependencyManager.SQL_EXCEPTION_PERMISSION_DENIED_ON_DATABASE ||
                            sqlExpt.Number == SqlCacheDependencyManager.SQL_EXCEPTION_PERMISSION_DENIED_ON_USER ||
                            sqlExpt.Number == SqlCacheDependencyManager.SQL_EXCEPTION_NO_GRANT_PERMISSION) {
                        string error;

                        if (!disable) {
                            if (table != null) {
                                error = SR.Permission_denied_table_enable_notification;
                            }
                            else {
                                error = SR.Permission_denied_database_enable_notification;
                            }
                        }
                        else {
                            if (table != null) {
                                error = SR.Permission_denied_table_disable_notification;
                            }
                            else {
                                error = SR.Permission_denied_database_disable_notification;
                            }
                        }

                        if (table != null) {
                            throw new HttpException(
                                SR.GetString(error, table));
                        }
                        else {
                            throw new HttpException(
                                SR.GetString(error));
                        }
                    }
                    else if (sqlExpt.Number == SqlCacheDependencyManager.SQL_EXCEPTION_ADHOC &&
                            sqlExpt.Message == SqlCacheDependencyManager.SQL_CUSTOM_ERROR_TABLE_NOT_FOUND) {
                        Debug.Assert(!disable && table != null, "disable && table != null");
                        throw new HttpException(SR.GetString(SR.Cache_dep_table_not_found, table));
                    }
                }

                string  errString;

                if (sqlCmd != null && sqlCmd.CommandText.Length != 0) {
                    errString = SR.GetString(SR.Cant_connect_sql_cache_dep_database_admin_cmdtxt,
                                    sqlCmd.CommandText);
                }
                else {
                    errString = SR.GetString(SR.Cant_connect_sql_cache_dep_database_admin);
                }

                if (throwError) {
                    throw new HttpException(errString, e);
                }
            }
            finally {
                if (sqlConnection != null) {
                    sqlConnection.Close();
                }
            }
        }

        public static void EnableNotifications(string connectionString) {
            SetupNotifications(0, null, connectionString);
        }

        public static void DisableNotifications(string connectionString) {
            SetupNotifications(SETUP_DISABLE, null, connectionString);
        }

        public static void EnableTableForNotifications(string connectionString, string table) {
            SetupNotifications(SETUP_TABLE, table, connectionString);
        }

        public static void EnableTableForNotifications(string connectionString, string[] tables) {
            if (tables == null) {
                throw new ArgumentNullException("tables");
            }

            foreach (string table in tables) {
                SetupNotifications(SETUP_TABLES, table, connectionString);
            }
        }

        public static void DisableTableForNotifications(string connectionString, string table) {
            SetupNotifications(SETUP_TABLE|SETUP_DISABLE, table, connectionString);
        }

        public static void DisableTableForNotifications(string connectionString, string[] tables) {
            if (tables == null) {
                throw new ArgumentNullException("tables");
            }

            foreach (string table in tables) {
                SetupNotifications(SETUP_TABLES|SETUP_DISABLE, table, connectionString);
            }
        }

        static string[] GetEnabledTables(string connectionString) {

            SqlDataReader       sqlReader = null;
            SqlConnection       sqlConn = null;
            SqlCommand          sqlCmd = null;
            ArrayList           tablesObj = new ArrayList();

            try {
                sqlConn = new SqlConnection(connectionString);
                sqlConn.Open();

                sqlCmd = new SqlCommand(SQL_QUERY_REGISTERED_TABLES_SP_DBO, sqlConn);
                sqlCmd.CommandType = CommandType.StoredProcedure;

                sqlReader = sqlCmd.ExecuteReader();

                while(sqlReader.Read()) {
                    tablesObj.Add(sqlReader.GetString(0));
                }
            }
            catch (Exception e) {
                SqlException sqlExpt = e as SqlException;

                if (sqlExpt != null &&
                    sqlExpt.Number == SqlCacheDependencyManager.SQL_EXCEPTION_SP_NOT_FOUND) {

                        throw new DatabaseNotEnabledForNotificationException(
                                SR.GetString(SR.Database_not_enabled_for_notification,
                                                                sqlConn.Database));
                }
                else {
                    throw new HttpException(SR.GetString(SR.Cant_get_enabled_tables_sql_cache_dep), e);
                }
            }
            finally {
                try {
                    if (sqlReader != null) {
                        sqlReader.Close();
                    }

                    if (sqlConn != null) {
                        sqlConn.Close();
                    }
                }
                catch {
                }
            }

            return (string[])tablesObj.ToArray(Type.GetType("System.String"));
        }

        public static string[] GetTablesEnabledForNotifications(string connectionString) {
            return GetEnabledTables(connectionString);
        }
    }
}


text:
import urllib2

url="http://dldir1.qq.com/qqfile/qq/QQ7.1/14522/QQ7.1.exe"
def get_file_size(url):
    opener = urllib2.build_opener()
    request = urllib2.Request(url)
    request.get_method = lambda: 'HEAD'
    try:
        response = opener.open(request)
        response.read()
    except Exception, e:
        print '%s %s' % (url, e)
    else:
        return dict(response.headers).get('content-length', 0)
def download(url,start_size):
    req = urllib2.Request(url)
    req.headers['Range'] = 'bytes=%d-%d'%(start_size,end_size)
    f = urllib2.urlopen(req)
    offset = start_size

if __name__ == '__main__':
    num =  get_file_size(url)
    print num


text:
module SocialTokenizer
  def self.configure(configuration = SocialTokenizer::Configuration.new)
    if block_given?
      yield configuration
    end
    @@configuration = configuration
  end

  def self.configuration
    @@configuration ||= SocialTokenizer::Configuration.new
  end

  class Configuration
    attr_accessor :lang

    def initialize
      self.lang = :en
    end
  end
end