Question: How do I fill a textbox with text if it is empty? I am using VB.NET.

Answer: 
It looks like you're describing a **cue banner**, which is prompt text that is displayed in an empty textbox. As of Windows XP, this functionality is natively supported by the operating system. The effect achieved doing it this way is much more elegant than setting the default text yourself in the `TextChanged` event. It looks like this:

     ![sample of textbox with cue banner text](https://i.stack.imgur.com/daXDW.jpg)

Setting this up is accomplished at the level of the Windows API by sending the textbox control an [`EM_SETCUEBANNER` message](http://msdn.microsoft.com/en-us/library/bb761639.aspx). To use this from a .NET project, you will have to use P/Invoke.

Fortunately, most of the work has already been done for you. [This sample project](http://www.codeproject.com/kb/edit/cueprovider.aspx) is a quick and painless way to add cue banner support to an existing project. [Here's another sample](http://www.ageektrapped.com/blog/the-missing-net-1-cue-banners-in-windows-forms-em_setcuebanner-text-prompt/), with a more complete explanation of the process.

If you don't want your application to depend on an external DLL, you can add the necessary code directly to your project. The simplest way is to subclass the existing `TextBox` control, and add the code to support cue banners there. See [this answer](https://stackoverflow.com/questions/4902565/watermark-textbox-in-winforms/4902969#4902969) for the code you'll need. If you have trouble converting it to VB.NET, try [this tool](http://www.developerfusion.com/tools/convert/csharp-to-vb/).
I assume you meant to add text from the aspx page.

```
<asp:TextBox ID="TextBox1" runat="server" value="Default Value"></asp:TextBox

```

Even when .NET don't suggest this feature in the intellitext, I assume that it will allow you to put any attribute, even custom that you can manipulate data in it. But, it does the work. and the value attribute is sent to the browser, therefore, initiate in the text field.

For TextArea (TextMode="MultiLine"), you can put between the tags.

```
<asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine">Text Here will be inside the TextArea</asp:TextBox>

```

It is like html textarea tag behave.