javascript - ClientScript.RegisterStartupScript not working -

i have searched & google, can't seem work. code in codebehind click event of "cancel" button in asp.net application not seem close popup window. ideas?

try {     if (btncancel.text == "close")     {         string csname1 = "popupscript";         type cstype = this.gettype();          clientscriptmanager cs = page.clientscript;         if (!cs.isclientscriptblockregistered(cstype, csname1))         {             clientscript.registerstartupscript(gettype(), "closepopup", "window.close();", true);         }     } }   

update: after postback, when @ source page, code see related is:

//<![cdata[ (function() {var fn = function() {$get("toolkitscriptmanager1_hiddenfield").value = '';sys.application.remove_init(fn);};sys.application.add_init(fn);})();window.close(); document.getelementbyid('validationsummary1').dispose = function() {     array.remove(page_validationsummaries, document.getelementbyid('validationsummary1')); } 

you can use instead

scriptmanager.registerstartupscript(this.page, gettype(), "closepopup", "window.close();", true); 

or can try one

page.clientscript.registerclientscriptblock(typeof(page), "closepopup", "window.close();", true); 

have day.