private void OKButton_Click(object sender, RoutedEventArgs e)
 {
     if (!String.IsNullOrEmpty(txtTienNghi.Text.Trim()))
     {
         TienNghiClient = new TienNghiSVCClient();
         if (TienNghiID == -1)
         {
             TienNghiClient.TienNghi_AddCompleted += new EventHandler<System.ComponentModel.AsyncCompletedEventArgs>(TienNghiClient_TienNghi_AddCompleted);
             TienNghiClient.TienNghi_AddAsync(txtTienNghi.Text, 0);
         }
         else
         {
             TienNghiClient.TienNghi_EditCompleted += new EventHandler<System.ComponentModel.AsyncCompletedEventArgs>(TienNghiClient_TienNghi_EditCompleted);
             TienNghiClient.TienNghi_EditAsync(TienNghiID, txtTienNghi.Text, 0);
         }
     }
     else
     {
         MessageBox.Show("Kiểm tra lại các trường bắt buộc nhập", "Thông báo", MessageBoxButton.OK);
     }
 }