WPF DataGrid Problem when hidden and Reshown in Editing Mode

public class DataGridBehaviors
{
  // The purpose of this property is to be able to signal a datagrid manually 
  // to end its editing mode. When you have datagrid on a tab inside a tabcontrol
  // based on content templates and a observablecollection as source, it may cause an
  // exception when leaving and reentering it in editing mode (while the caret is in 
  // a cell)
#region EndEditing Property
  // When starting this property, I first tried to generate an action right here and 
  // call it from the viewmodel. This didn't work out so I went for having a simple
  // bool which - when flipped - signals the datagrid to stop the editing mode.
  
  public static void SetEndEditing(DependencyObject obj, bool a)
  {
    obj.SetValue(EndEditingProperty, a);
  }

  public static bool GetEndEditing(DependencyObject obj)
  {
    return (bool) obj.GetValue(EndEditingProperty);
  }

  public static readonly DependencyProperty EndEditingProperty
    = DependencyProperty.RegisterAttached(
    "EndEditing",
    typeof(bool),
    typeof(DataGridBehaviors),
    new PropertyMetadata(new PropertyChangedCallback(EndEditingChanged))
  );

  private static void EndEditingChanged(DependencyObject sender, 
    DependencyPropertyChangedEventArgs e)
  {
    var dg = sender as DataGrid;
    if (null == dg) return;

    // CancelEdit is not sufficient
    dg.CancelEdit();
    // this has also to be called to really end the editing mode
    dg.CommitEdit();
  }
#endregion
}