Ajax Manager Not Run

[trunghieu]

Hi , i'm student , i have some problem with ajax manager,when i click to btnclick button ,the code will run until RadGrid2.DataSource = qt.DanhSachDoiQua(makh); , but i must reload my site then
it updated into RadGrid2 

 this's my code

<telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" Runat="server"
                   Skin="Default" >
               </telerik:RadAjaxLoadingPanel>
               <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server"
                   DefaultLoadingPanelID="RadAjaxLoadingPanel1" EnableAJAX="true" >
                   <AjaxSettings >
                         <telerik:AjaxSetting  AjaxControlID="btnclick"  >
                           <UpdatedControls>
                               <telerik:AjaxUpdatedControl ControlID="RadGrid2"   />
                           </UpdatedControls>
                       </telerik:AjaxSetting>
                   </AjaxSettings>
               </telerik:RadAjaxManager>

protected void btnclick_Click(object sender, EventArgs e)
{
    qt = new global::sieuthi.BUSINESS.B_quatang();
    foreach (GridDataItem item in RadGrid1.SelectedItems)
    {
        string strKey = "";
        string sl = "";
        //  TextBox tb = (TextBox)item.TemplateControl.FindControl("txtsl");//.GetDataKeyValue("txtsl").ToString();
        try
        {
            strKey = item.GetDataKeyValue("ID").ToString();
            sl = txtsoluong.Text.Trim();
            qt.addQuatang(makh, strKey, int.Parse(sl));
        }
        catch (Exception ex)
        {
            lbloi.Text = ex.Message;
            //khach2 hàng @KH đã có trong DS tặng quà của sự kiện @sukien Nam @nam ==>bo sung gap
        }
    }
    RadGrid2.DataSource = qt.DanhSachDoiQua(makh);
}

[Cori]

Try calling RadGrid2.DataBind(); after you set the DataSource.