private void txtBarCodeNum_KeyUp(object sender, KeyEventArgs e)

         {

             TxtInt(sender as TextBox);

         }

         private void txtBarCodeNum_TextChanged(object sender, TextChangedEventArgs e)

         {

             TxtInt(sender as TextBox);

         }

         private void TxtInt(TextBox txt)

         {

             if (txt==null || string.IsNullOrEmpty(txt.Text))

             {

                 txt.Tag = "";

                 return;

             }

             try

             {

                 txt.Text = txt.Text.Trim();

                 txt.Tag = Convert.ToInt32(txt.Text); ;

             }

             catch

             {

                 if (txt.Tag==null)

                 {

                     txt.Text = "";

                 }

                 else

                 {

                     txt.Text = txt.Tag.ToString();

                 }

             }

             txt.SelectionStart = txt.Text.Length;

         }