yes, i got it
the solution of this question is
Change:
<ajaxToolkit:ToolkitScriptManager ID="ScriptManager1" runat="server" />
to:
<asp:ScriptManager ID="ScriptManager1" runat="server" />
but also remember that ajaxcontroltoolkit version should match
for vs 2010 use ajaxcontroltoolkit 4.0 and
for vs 2008 use ajaxcontroltoolkit 3.5 and 3.0(rare cases)
i have use vs 2008 and ajaxcontroltoolkit 3.5 but it doesn't work so i installed
ajaxcontroltoolkit 3.0...now it works well....
thanks for all your post buddies