System.InvalidOperationException
The solution is quite simple you need to notify ASP.Net that not to validate the event by setting the EnableEventValidation flag to FALSE.
RegisterForEventValidation can only be called during Render();
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.InvalidOperationException:
RegisterForEventValidation can only be called during Render();
You can set it in the Web.Config in the following way
<pages enableEventValidation ="false"></pages>
This will apply to all the pages in your website. Else you can also set it in the @Page Directive of the page on which you are experiencing the above error.
<%@ Page Language="C#" AutoEventWireup="true" EnableEventValidation = "false" >
