MVVM in WPF how to communicate with the viewmodel

Question

I guess I am still a little hazy on how communication goes in MVVM. I read that you are not supposed to use events to communicate with the viewmodel, so i assume that you send a command.

However, commands actually bubble up within the visual tree (the view), right? so then it may reach some target control that can handle the command. Does that target control then have a viewmodel that can modify the model?

Sorry, I'm really confused about how to get commands from the view to the model. I assume that getting information the other way is just a simple matter of having the model implement Inotifypropertychanged to tell the viewmodel that it has changed and then have the viewmodel implement inotifypropertychanged so that the view can bind to the viewmodel and have the properties update.

http://blogs.msdn.com/blogfiles/erwinvandervalk/WindowsLiveWriter/ImplementingtheModelViewViewModelpattern_D996/image_14.png

Answer 1

Not all commands bubble - those are RoutedUICommands, which are just a particular implementation of the ICommand interface provided by the framework. You can implement your own ICommand objects that have custom behavior and act just like normal objects (no bubbling, tunneling). If you create them in your ViewModel, certain View objects like Buttons and MenuItems can bind directly to them through their 'Command' properties.