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copied!<p>The RelayCommand isn't a RoutedCommand, which I think is where you ending up confused.</p> <p>The constructors for the Relay command take an <a href="http://msdn.microsoft.com/en-us/library/018hxwa8.aspx" rel="nofollow noreferrer">Action delegate</a> and optional <a href="http://msdn.microsoft.com/en-us/library/bfcke1bz.aspx" rel="nofollow noreferrer">Predicate delegate</a>. These delegates don't take an EventArgs, just the single Object parameter, which is why you are encountering an error. The predicate also requires a return type of bool, which is the next error you'll get. In the CanExecute predicate instead of setting e.CanExecute like you do with a RoutedCommand you simply return true/false.</p> <p>Here's how it should look:</p> <pre><code>public ICommand RelayCommand_MoveUp { get { if (_relayCommand_MoveUp == null) { _relayCommand_MoveUp = new RelayCommand(Execute_MoveUp, CanExecute_MoveUp); } return _relayCommand_MoveUp; } } private void Execute_MoveUp(object sender) { if (_selectedFolder != null) { _selectedFolder.SelectParent(); } } private void CanExecute_MoveUp(object sender) { return (_selectedFolder != null) && (_selectedFolder.Parent != null); } </code></pre> <p><br/><br/> <strong>EDIT (Added from discussion in comments):</strong></p> <p>If you want to use something more like the RoutedCommands, which will make the ViewModels more dependent on WPF specific views, there are some good options available.</p> <p>This <a href="http://groups.google.com/group/wpf-disciples/browse_thread/thread/40f387caac2f1e13?pli=1" rel="nofollow noreferrer">discussion</a> got the whole idea of using RoutedCommands in conjunction with MVVM started.</p> <p>And <a href="http://www.codeproject.com/KB/WPF/VMCommanding.aspx" rel="nofollow noreferrer">here's</a> a very solid solution to the issues presented by Josh Smith and Bill Kempf.</p>

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