sys.webforms.pagerequestmanagerservererrorexception

sys.webforms.pagerequestmanagerservererrorexception ERROR

ok, try another simplest way:

asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="false"
and also setting the EnableEventValidation="false"
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You may want to try setting ValidateRequest="false" in the Page declaration. It worked for me.