Let a TextBox in a web form pass the angle brackets.

To get away from errors that start out like like this:

A potentially dangerous Request.Form value was detected from the client...

 
 

Put this inside of system.web in Web.config:

<httpRuntime requestValidationMode="2.0" />

 
 

And put this...

ValidateRequest="false"

 
 

...inside of that topmost line of the .aspx markup that looks like:

<%@ Page Language="C#" CodeBehind="Foo.aspx.cs"...

 
 

By the way this suggested that you should use window.escape and window.unescape in JavaScript to just doctor up TextBox's contents in advance of a post-to-self in lieu of opening a security hole pagewide. I have not tried it. I found it interesting.