Question: I'm writing a CMS in ASP.NET/C#, and I need to process things like that, every page request:

```
<html>
<head>
    <title>[Title]</title>
</head>
<body>
    <form action="[Action]" method="get">
        [TextBox Name="Email", Background=Red]
        [Button Type="Submit"]
    </form>
</body>
</html>

```

and replace the [...] of course.

My question is how should I implement it, with ANTLR or with Regex? What will be faster? Note, that if I'm implementing it with ANTLR I think that I will need to implement XML, in addon to the [..]. 

I will need to implement parameters, etc.

**EDIT:** Please note that my regex can even look like something like that:

```
public override string ToString()
{
    return Regex.Replace(Input, @"\[
                                    \s*(?<name>\w+)\s*
                                    (?<parameter>
                                        [\s,]*
                                            (?<paramName>\w+)
                                            \s*
                                            =
                                            \s*
                                            (
                                                (?<paramValue>\w+)
                                                |
                                                (""(?<paramValue>[^""]*)"")
                                            )
                                    )*
                               \]", (match) =>
                                  {
                                      ...
                                  }, RegexOptions.IgnorePatternWhitespace);
}        

```

Answer: 
Whether the correct tool is RegEx or ANTLR or even something else entirely should be heavily dependent on your **requirements**. The best answer to a "what tool to use" question shouldn't be primarily based on *performance*, but on *the right tool for the job*.

RegEx is a text search tool. If all you need to do is pull strings out of strings then it's often the hammer of choice. You'll likely want a tool to help you build your RegEx. I'd recommend [Expresso](http://www.ultrapico.com/ExpressoDownload.htm), but there are lots of options out there.

ANTLR is a compiler generator. If you need error messages and parse actions or any of the complicated things that come with a compiler then it's a good option.

What it looks like you're doing is XML search/replace, have you considered XPath? That would be my suggestion.

Choosing the right tool for the job is definitely important, something that should be researched and thought out before development begins. In all cases, it's important to fully understand the program requirements before making any decisions. Do you have a specification for the project? If not, spending the time to come up with one will save you all the time that a poor tool choice can cost you.

Hope that helps!
If the language you are parsing is **regular** then **regular expressions** are certainly an option. If it is not then ANTLR may be your only choice. If I understand these matters correctly XML is not regular.