function not getting called during autopostback

Hi,

  I have two combo boxes in an aspx page.
<asp:DropDownList ID="drpCategory" runat="server"
Font-Names="Verdana" Font-Size="8pt"
Width="138px" AutoPostBack="True"
OnSelectedIndexChanged="drpCategory_SelectedIndexChanged"
OnTextChanged="drpCategory_SelectedIndexChanged">
</asp:DropDownList>

 
<asp:DropDownList ID="drpSubcategory" runat="server" Font-Names="Verdana" Font-Size="8pt"
                    Width="138px" >
                </asp:DropDownList>
 
I need to populate the drpSubcategory depending on the value chosen from drpCategory. As you can see i ...