MVVMLight具有相应视图的多个instancekeyed-ViewModels

Question

it might be a dump subject-title, but I don't know how to summarize this problem.

First of all, I'm new to MVVM and MVVMLight.

I'm trying to create several instances of a specific viewmodel (eg GalleryViewModel) and display the corresponding data in a corresponding view, bound to a specific instance of a GalleryViewModel. So the user has (eg) five GalleryViews open, while in the background each GalleryView must be bound to the corresponding GalleryViewModel.

Therefore, I call "GetInstance" of the SimpleIoC with a GUID as InstanceKey.

The problem is, that that way, the view doesn't get updated, when the data in the viewmodel changes. I found out, that this is only the case, when I instanciate the viewmodel with an instance key.

So I think, i have to link/bind that current view to that viewmodel with instancekey XY. But I don't know how to do it.

My "architecture" is like that: The MainViewModel calls the GetInstance(GUID)-Method. Within the MainView, a new UserControl gets displayed/created with the GalleryView. Its datacontext is bound to GalleryViewModel via XAML (but this might be the problem, because this binding can't know the GUID, so it might get bound to a wrong instance (?) and the DataBindings don't get updated.

Here is some code:

The ViewModelLocator returns only one instance (maybe that's the problem)

public GalleryMainViewModel Gallery
{
    get { return ServiceLocator.Current.GetInstance<GalleryMainViewModel>(); }
}

From within the MainViewModel the "navigation" gets called (although my application lacks of a NavigationInterface (right now).

private void DoOpenTab(string windowname, string payload = null)
        {
            DockWindowViewModel window;
            string guid;            
            switch(windowname)
            {                    
                case "Gallery":
                    guid = Guid.NewGuid().ToString();
                    window = ServiceLocator.Current.GetInstance<GalleryMainViewModel>(guid);
                    window.ViewModelInstanceKey = guid; 
                    Messenger.Default.Send(
                        new NotificationMessage(payload), 
                        (window as GalleryMainViewModel).MessageToken);
                    DockManagerViewModel.AddDocument(window);
                    break;
            }
        }

And the GalleryView (which is a UserControl that is being placed within an Avalon DockManager-Tab), looks like this

<src:PluginView
    DataContext="{Binding Gallery, Source={StaticResource Locator}}"
    <!-- just normal bindings. -->
</src:PluginView>

I hope, someone can help me a bit. I'm feeling really close to the solution, but I really don't know how to solve it completly.

Thanks in advance!

Answer 1

If this is in your Locator

   public GalleryMainViewModel Gallery
    {
        get { return ServiceLocator.Current.GetInstance<GalleryMainViewModel>(); }
    }

And this is in your View

<src:PluginView
    DataContext="{Binding Gallery, Source={StaticResource Locator}}"
    <!-- just normal bindings. -->
</src:PluginView>

Then the VM created using the guid is potentially never bound to the view. It would depend on what happens when the notification message is recived by the view.

The above code tells the view to get its DataContext directly from the locator via the Gallery property. Which as you stated will be the same instance for all instances of this view.