How to bind application commands to view model(WPF)?

Question

I have already read Josh Smiths article about binding commands to view model using RelayCommand. However I need to bind ApplicationCommands.Save to a view model so that when a user clicks the save menu item it is handled in the window. How is it possible?

Answer 1

The best solution I'm aware of us to use a service. For example, an ICommandBindingsProvider like this:

public interface ICommandBindingsProvider
{
    CommandBindingCollection CommandBindings { get; }
}

This gets injected into your ViewModel and used like this:

public MyViewModel(ICommandBindingsProvider commandBindings)
{
    commandBindings.Add(new CommandBinding(....));
}

How the service gets injected will be dependent on what MVVM framework you're using. Most (but not all) support some sort of service injection capabilities. If you need a more concrete code example, look at Onyx which does service injection and has a service that does just this.

Answer 2

There is a good tutorial to help bind application commands.

1. Setup your command binding collection for your view to bind to in your view model. e.g.:

public CommandBindingCollection CommandBindings { get; }

public YourViewModel()
{
//Create a command binding for the save command
var saveBinding = new CommandBinding(ApplicationCommands.Save, SaveExecuted, SaveCanExecute);

//Register the binding to the class
CommandManager.RegisterClassCommandBinding(typeof(YourViewModel), saveBinding);

//Adds the binding to the CommandBindingCollection
CommandBindings.Add(saveBinding);
}

1. Setup attached properties. Read the article on how to do that.

2. Then bind to it using attached properties.

<UserControl local:AttachedProperties.RegisterCommandBindings="{Binding CommandBindings}"> 
    <Window.DataContext>
        <local:YourViewModel></local:YourViewModel>
    </Window.DataContext>
</UserControl>