Question

I have a Multiline Textbox. I donot want to let user type HTML Tags or validation can be done in the server side. Any suggestions?

When I set ValidateRequest="true" it throws error

potentially dangerous Request.Form value was detected from the client

This is also not required. I tried to put validation by checking the character < but this is also not a proper validation because you can type like <kanavi and this is not a HTML tag

Answer 1

set ValidateRequest="false"

and handle on the server if there is a tag in input show message.

you can remove the tags

 Regex.Replace(source, "<.*?>", string.Empty);

OR you use encoding if you want to keep them