On Export to Excel having problem on second Click

client side in HTML Tag add

OnClientClick="_spFormOnSubmitCalled = false;_spSuppressFormOnSubmitWrapper=true;"


Example


<asp:Button ID="btnExportToExcel" runat="server" Text="Export to Excel" onclick="btnExportToExcel_Click" OnClientClick="_spFormOnSubmitCalled = false;_spSuppressFormOnSubmitWrapper=true;" />