 <p>If you are using an unpatched .net 4.5. Microsoft broke the <code>.CanExecute</code> event.</p> <p><a href="http://connect.microsoft.com/VisualStudio/feedback/details/753666/net-4-0-application-commands-canexecute-not-updating-in-4-5" rel="nofollow">http://connect.microsoft.com/VisualStudio/feedback/details/753666/net-4-0-application-commands-canexecute-not-updating-in-4-5</a></p> <p>If you are using the <code>RelayCommand</code> from <a href="http://msdn.microsoft.com/en-us/magazine/dd419663.aspx#id0090030" rel="nofollow">http://msdn.microsoft.com/en-us/magazine/dd419663.aspx#id0090030</a> and are not raising the CanExecuteChanged event when redoStack changes.</p>