private void cmbConstraintType_SelectedIndexChanged(object sender, EventArgs e)
 {
     PropertyValueConstraintType ctype = (PropertyValueConstraintType)cmbConstraintType.SelectedItem;
     switch (ctype)
     {
         case PropertyValueConstraintType.PropertyValueConstraintType_Range:
             {
                 RangeConstraintSettingsCtl ctl = new RangeConstraintSettingsCtl();
                 ctl.Dock = DockStyle.Fill;
                 grpSettings.Controls.Clear();
                 grpSettings.Controls.Add(ctl);
             }
             break;
         case PropertyValueConstraintType.PropertyValueConstraintType_List:
             {
                 ListConstraintSettingsCtl ctl = new ListConstraintSettingsCtl();
                 ctl.Dock = DockStyle.Fill;
                 grpSettings.Controls.Clear();
                 grpSettings.Controls.Add(ctl);
             }
             break;
     }
 }