ASP.NET Webforms - "A potentially dangerous Request.Form value was detected from the client"

Question

I'm getting the following error when I submit html in a textarea "A potentially dangerous Request.Form value was detected from the client." How do I disable this type of security validation to just one field and not the entire page/website. What I do NOT want to do is set validateRequest to false for an entire page/website.

EDIT: I need a solution for .NET Framework 3.5

Answer 1

In .NET 4.5 you can use the ValidateRequestMode property to exclude fields from Request Validation.

However in .NET 4 and Lower this cannot be done, and you must either validate the entire request or not.