protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
 {
     if (e.CommandName == "Delete")
     {
         // get the categoryID of the clicked row
         int leaveID = Convert.ToInt32(e.CommandArgument);
         lvDb.DeleteLeave(leaveID);
         Response.Redirect(Request.RawUrl);
     }
 }