Showing another View from my current Viewmodel and closing a view from my viewmodel?

Question

I have another view setup and ready and waiting with its viewmodel. My RelayCommand arrives in my "Current" viewmodel. What is the best way to show the new view from my current viewmodel?

I have been reading and it appears that I need to use the Messenger to send a message from my viewmodel to ??? my new viewmodel that is associated with my view I wish to show? But how would I show the View?

Also is there a way to support closing a view from a viewmodel? I wonder if mvvm-light brings anything extra to the table - ie.. Triggers to force the viewmodel to close the view?

its currently WPF but i was hoping for the same functionality for silverlight — Martin, May 04 '11 at 05:00

score 3 · Accepted Answer · answered May 04 '11 at 10:21

In WPF, you have two ways (out of the box) for "showing"/"closing" views. The first, is simply, by showing a Window, or Dialog via the .Show() or .ShowDialog() methods, and they can be closed with the .Close() method. In this case, you can use the MVVMLight Messenger class as you mentioned to send the show/close messages to the view in a decoupled way. here's an example with "closing".

In the ViewModel:

CloseTheView()
{
    Messenger.Default.Send(new CloseTheViewMessage);
}

in the code-behind of your view:

//Constructor
public TheView()
{
    ...
    Messenger.Default.Register<CloseTheViewMessage>( () => this.Close() );
}

as you can see, this involves some code in the code-behind file, but it's no big deal, since it's just one line of functionality.

The second approach is to use the Navigation Framework (which is available for both WPF and Silverlight). You define a "Shell" which is the main Window (or UserControl), you put a frame inside of it, and you make your other views inherit from Page, and then initiate the navigation from your ViewModel using the instance of the NavigationService associated with Frame (or directly the one associated with the page itself).

Hope this helps :)

Showing another View from my current Viewmodel and closing a view from my viewmodel?

1 Answers1