DataGrid内绑定DropDownList

private   void  dg_Class_ItemDataBound( object  sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
         {
            string SqlSelect = "select dep_id,dep_name,dep_code from db_dep";
            if(e.Item.ItemType==ListItemType.EditItem)
            {
                DropDownList DDLinDG = (DropDownList)(e.Item.FindControl("ddl_depnameInDG"));
                DDLinDG.DataSource = NN.ds(SqlSelect).Tables[0];
                DDLinDG.DataValueField = "dep_id";
                DDLinDG.DataTextField = "dep_name";
                DDLinDG.DataBind();
                DDLinDG.Items.FindByText(Convert.ToString(DataBinder.Eval(e.Item.DataItem,"dep_name"))).Selected=true;
            }
        }