private void RadDataForm_EditEnding(object sender, Telerik.Windows.Controls.Data.DataForm.EditEndingEventArgs e)
  {
      var dataForm = (RadDataForm)sender;
      var myField = dataForm.ChildrenOfType<DataFormDataField>().FirstOrDefault(df => df.Name == "myField");
      if (myField != null)
      {
          var comboBox = (RadComboBox)myField.Content;
          comboBox.DataContext = null;
      }
  }