winform中TextBox只能输入字母

  private void txtTestPerson_KeyPress(object sender, KeyPressEventArgs e)

         {

             if ((e.KeyChar >= 'a' && e.KeyChar <= 'z') || (e.KeyChar >= 'A' && e.KeyChar <= 'Z') || e.KeyChar == '\b')

             {

                 e.Handled = false;

             }

             else

             {

                 e.Handled = true;

             }

         }