button click not working inside updatepanel

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C#

ASP.NET

C#4.0

i am adding buttons dynamicaly to repeater.. button displays well.. but when i click button event does not get fired.. i tried both OnCLick of button and comamndname of button (so that i can have itemcommand of repeater..) but both wrere in vain.. Kindly assist me.. Thanks...

just a piece of code here.. but not complete.. forgive me..

"<span>" + lstFlightSegment[i].Attribute("Duration").Value + "</span></div><div class=\"duration_time_mid\">" + StopOver + "</div>" +
   "</td><td class=\"fare_tab1\"><div class=\"fare_tab_top\"><span>Rs</span> " + totalFare + "</div><div class=\"fare_tab_btm\">Inclusive of all Taxes</div></td>" +
   "<td class=\"book2\"><div class=\"book1_top\"><div runat=\"server\" id=\"mydiv\">" + ControlRenderToString(btn) + "</div>"

ControlRenderToString(btn)

method displays button in every item of item template