<telerik:RadDropDownTree RenderMode="Lightweight" ID="RadDropDownTree3" runat="server" Width="300px" DefaultMessage="Please select"
            DataFieldID="EmployeeID" DataFieldParentID="ReportsTo" DataTextField="LastName"
            DataSourceID="SqlDataSource1">
        </telerik:RadDropDownTree>
      
        <asp:SqlDataSource runat="server" OnSelecting="SqlDataSource1_Selecting" ID="SqlDataSource1" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"
            SelectCommand="SELECT * From Employees"></asp:SqlDataSource>

protected void SqlDataSource1_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
{
    Label1.Text += "<br /> Sql request at:" + DateTime.Now.ToLongTimeString();
}