RegisterForEventValidation can only be called during Render()

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The following is the screen shot which you get due to this error:

This error occurs whenever we are trying to render control to response. To fix this problem I have added EnableEventValidation="false" to @Page directive of aspx page.

This will look like as follows:

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" EnableEventValidation="false" %>

This code will fix this issue.