http://ayende.comAyende @ RahienCopyright (C) Ayende Rahien 2004 - 2021 (c) 202660Fair point :) http://ayende.com/4113/conditions-and-facts#comment10http://ayende.com/4113/conditions-and-facts#comment10Thu, 20 Aug 2009 12:16:42 GMTMike, I wouldn't call 2 if statements all over, but yes, I could have done that http://ayende.com/4113/conditions-and-facts#comment9http://ayende.com/4113/conditions-and-facts#comment9Thu, 20 Aug 2009 12:10:27 GMTCould you possibly make the Command code even simpler if you used the Null Value Pattern to have your infrastructure insert a Fact that is always true instead of checking for null all over? http://ayende.com/4113/conditions-and-facts#comment8http://ayende.com/4113/conditions-and-facts#comment8Thu, 20 Aug 2009 11:48:13 GMTYes, I have seen that. http://ayende.com/4113/conditions-and-facts#comment7http://ayende.com/4113/conditions-and-facts#comment7Mon, 10 Aug 2009 16:56:06 GMTAyende, Have you looked into the new Rx Framework which seems to be doing similar things over Linq? [themechanicalbride.blogspot.com/.../...events.html](http://themechanicalbride.blogspot.com/2009/07/introducing-rx-linq-to-events.html)http://ayende.com/4113/conditions-and-facts#comment6http://ayende.com/4113/conditions-and-facts#comment6Mon, 10 Aug 2009 15:39:23 GMTI used this: public class ActionCommand : ICommand { readonly Action <object Action; public event EventHandler CanExecuteChanged; public ActionCommand(Action <object action) { Action = action; Enabled = true; } bool enabled; public bool Enabled { get { return enabled; } set { enabled = value; var canExecuteChanged = CanExecuteChanged; if (canExecuteChanged != null) canExecuteChanged(this, EventArgs.Empty); } } public bool CanExecute(object parameter) { return Enabled; } public void Execute(object parameter) { if (Action != null) Action(parameter); } } >http://ayende.com/4113/conditions-and-facts#comment5http://ayende.com/4113/conditions-and-facts#comment5Mon, 10 Aug 2009 13:57:39 GMTMichael, CompositeObservable to to rescue http://ayende.com/4113/conditions-and-facts#comment4http://ayende.com/4113/conditions-and-facts#comment4Mon, 10 Aug 2009 13:51:47 GMTStephen, Fact implementing INPC means that I can bind directly to it http://ayende.com/4113/conditions-and-facts#comment3http://ayende.com/4113/conditions-and-facts#comment3Mon, 10 Aug 2009 13:51:01 GMTWhat if the condition is based on more than one observable? Say for example, CurrentPage < TotalPages-1? How would you subscribe to both? http://ayende.com/4113/conditions-and-facts#comment2http://ayende.com/4113/conditions-and-facts#comment2Mon, 10 Aug 2009 11:43:43 GMTI like it, you basically encapsulate a condition and manage handling its invalidation. Although I'm not sure you need fact to be INotifyPropertyChanged, you could well just have a bog standard 'Changed' event. Fact is nice and short as a class name but something niggles at me regarding a fact changing.. to me its more like an ObservableCondition, but obviously that doesnt sound as good ;). http://ayende.com/4113/conditions-and-facts#comment1http://ayende.com/4113/conditions-and-facts#comment1Mon, 10 Aug 2009 10:55:57 GMT