Binding to a DropDown list in a Footer Row

I typically use a separate ObjectDataSource that I place outside the GridView for clarity and easy of access in the CodeBehind. Alternatively, you could load it by hand using FindControl or declaring an OnLoad handler.

<footertemplate>
    <asp:DropDownList ID="inDataAssetIDFooter" runat="server" DataSourceID="dsDataAsset" 
        DataValueField="ID" DataTextField="Name" CssClass="DropDownList" AppendDataBoundItems="true">
        <asp:ListItem Value="0">Select Data Asset</asp:ListItem>
    </asp:DropDownList>
    <asp:CompareValidator ID="vldDANameFooter" runat="server" 
    Operator="GreaterThan" ValueToCompare="0" ControlToValidate="inDataAssetIDFooter" 
    Text="*" ErrorMessage="Data Asset is Required"/>
</footertemplate>

<asp:ObjectDataSource ID="dsDataAsset" runat="server" SelectMethod="GetUnRelatedDataAssetsByAppID"
    TypeName="MyProj.Lib.DataAssetDAL">
    <SelectParameters>
        <asp:QueryStringParameter Name="ID" QueryStringField="PID" Type="Int32" />
    </SelectParameters>
</asp:ObjectDataSource>