DropDown Not Working on 0 index

i have one dropdownlist which have sqldatasource.......
 
<asp:DropDownList ID="DropDownList5" runat="server" AutoPostBack="True" 
        DataSourceID="SqlDataSource3" DataTextField="Industry" 
        DataValueField="Industry" Height="16px" Width="69px">
 
    </asp:DropDownList>
 
when i click on first text of dropdown the autopostback no working....when i click on second it works......
please tell me how to postback on first text in dropdown.... 
 
thanks
Rahul kumar
 
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