//First in C# CS file call method
Buttonname.OnClientClick = "jsmethodname()";
//on ASPX page add following method
<script language="javascript" type="text/javascript">
function jsmethodname()
{
window.WebForm_OnSubmit = function ()
{ return true; };
}
</script>This code snippet for download file multiple time without postback. This we can use in Aspx pages and this method will cal in CS file
