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Drop down not causing postback on the first selection

Posted By:      Posted Date: October 03, 2010    Points: 0   Category :ASP.Net

hello i have a dropdown list

<asp:DropDownList ID="DDName" runat="server" AutoPostBack="True"
                                    DataSourceID="sdsName" DataTextField="Name" DataValueField="name_ID"

the problem that it is not causing post back on the first selection but on the second, I mean if i select from drop down list first selection no post back on the server,but when i select another item from the list (the second click on a different list item ) i have no problem

please help

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