DataGrid中嵌入DropDownList无法设置SelectIndex

以为是一个Bug。找了半天才发现，将SelectedValue=Category.ID错误写成SelectedValue=ID，巨汗！

<asp:TemplateColumn HeaderText="行业">
                                <ItemTemplate>
                                    <asp:Label id=Label1 runat="server" Text='<%# DataBinder.Eval(Container.DataItem,"CateGory.Name", "{0}") %>'>
                                    </asp:Label>
                                </ItemTemplate>
                                <EditItemTemplate>
                                    <asp:DropDownList id=drpColCategory runat="server" SelectedValue='<%# DataBinder.Eval(Container.DataItem,"CateGory.ID", "{0}") %>' DataSource="<%# TopCategory %>" DataValueField="ID" DataTextField="Name">
                                    </asp:DropDownList>
                                </EditItemTemplate>
                            </asp:TemplateColumn>

不过在无谓的问题查找当中，发现了一个奇怪的情况。aspx文件中如些定义

<EditItemTemplate>
    <asp:DropDownList id="drpColCategory" runat="server"></asp:DropDownList>
</EditItemTemplate>

并意图在ItemCreate事件中为DropDownList绑定数据及指定SelectedValue，SelectedValue似乎总被忽略掉，她始终选择第一项。相关代码如下

private void DataGrid1_ItemCreated(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
        {
            Control ctl = e.Item.FindControl("drpColCategory");
            if(ctl==null)
                return;
            if(e.Item.DataItem==null)//提交表格
                return;
            
            Entity.Advertisement ad = (Entity.Advertisement)e.Item.DataItem;
            this.listCategory((DropDownList)ctl,ad.CateGory.ID);
        }

private void listCategory(DropDownList pDropControl,int pCateID)
{
    Entity.Locator.CategoryLocator catLoc = new Mag.Entity.Locator.CategoryLocator(this.DbConnect);
    IList list = catLoc.SelectTops();
    pDropControl.DataSource = list;
    pDropControl.DataTextField = "Name";
    pDropControl.DataValueField = "ID";
    if(pCateID>-1)
        pDropControl.SelectedValue = pCateID.ToString();
    pDropControl.DataBind();
}