Question

I got a MasterPage UserControl which contain 3 user controls (and 3 viewmodels)

MasterView:
 -> MenuView (-> MenuViewModel )
 -> InfoView (-> InfoViewModel )
 -> SliderView (-> SliderViewModel )

In slider view i got a listbox with SelectedItem Property binded to a SelectedItem Property in the view model (SliderViewModel)

when the SelectedItem changes , i want to bubble it all the way to InfoViewModel and to update InfoView.

I can do it with events like i did many times in winforms but i’m looking for best practice way of the mvvm pattern.

another small question is , should i create a viewmodel for the MasterView page as well ? although it does not contain anything beside combining 3 users controls together.

your help will be greatly appreciated

Answer 1

I am not sure about the best MVVM best practise in this scenario but I can think of one way of doing it through MVVM.

You can create a MasterViewModel and expose a property in masterViewModel for communication between other view models. Like below

class MasterViewModel
{
    MenuViewModel;
    InfoViewModel;
    SliderViewModel;

    public CommunicationProperty 
    {
       set
       {
       InforViewModel.SomeProperty = value;
       }
    }
}

class SliderViewModel
{
    pubic SliderViewModel(MasterViewModel masterViewModel)
    {
        //hold reference of master view model in a variable  
    }

    public SelectedItem
    {
        set
        {
            // change the info view model via master view model
            masterViewModel.CommunicationProperty = value;
        }
    }
}