C# telerik grid cell value from template column

I have a grid-template-column defined like this( to save time and space i'll only put the column):

<telerik:GridTemplateColumn HeaderText="Id" Reorderable="true" SortExpression="Id" UniqueName="Id" DataField="Id">
                    <ItemTemplate>
                        <asp:Label ID="lblId" runat="server" T开发者_如何学JAVAext='<%# Eval("Id") %>' />
                    </ItemTemplate>
                    <EditItemTemplate>
                        <telerik:RadTextBox ID="txbId" Width="50px" runat="server" TextMode="SingleLine"
                            Text='<%# Bind("Id") %>' />
                    </EditItemTemplate>
                    <ItemStyle VerticalAlign="Top" />
             </telerik:GridTemplateColumn>

And I want on the PreRender event, to extract the value of this column

protected void RadGrid1_PreRender(object sender, System.EventArgs e)
    {
        //string selectedItem = ((GridDataItem)RadGrid1.SelectedItems[0])["Id"].Text;
        foreach (GridDataItem item in RadGrid1.Items)
        {
            //not working
            string k = item["Id"].Text;// is empty string 
            string key = (item["Id"].TemplateControl.FindControl("lblId") as RadTextBox).Text;// null pointer
}

Any idea how to fix it?

Thx a lot.

It seems that the solution is rather simple, responded on telerik forum:

foreach (GridDataItem item in grdHeader.EditItems)
            {
                // if in editing mode
                GridEditableItem edititem = (GridEditableItem)item.EditFormItem;
                RadTextBox txtHeaderName = (RadTextBox)edititem.FindControl("txbId");
                //otherwise
                Label lbl= (Label)edititem.FindControl("lblId");
                string id = lbl.Text;
            }

I could be mistaken (as I'm not super familiar with the Telerik control suite), but normally, data binding events don't occur until after the control's PreRender event. You'll have to DataBind earlier, or move your logic to later in the page life cycle.

Try

foreach (GridDataItem item in RadGrid1.Items)
    {
        if(item.ItemType == GridItemType.Item ||
                    item.ItemType ==   GridItemType.AlternatingItem)
        {
            string k = item["Id"].Text;// is empty string 
            ...