//------------------------------------------------------ // // Privte Methods // //------------------------------------------------------ #region Private Methods // Private helper that adds a new UIElementPropertyUndoUnit to the undo stack. private static void AddPrivate(ITextContainer textContainer, UIElement uiElement, DependencyProperty property, object newValue) { UndoManager undoManager = TextTreeUndo.GetOrClearUndoManager(textContainer); if (undoManager == null) { return; } object currentValue = uiElement.ReadLocalValue(property); if (currentValue is Expression) { // Can't undo when old value is an expression, so clear the stack. if (undoManager.IsEnabled) { undoManager.Clear(); } return; } if (currentValue.Equals(newValue)) { // No property change. return; } undoManager.Add(new UIElementPropertyUndoUnit(uiElement, property, currentValue)); }