CODEWITHSUNDEEP
c#wpfmvvmviewmodelhierarchy
Nicholas
Nicholas

Reputation: 3336

How do I nest multiple ViewModels in a top level ViewModel, in a sort of hierarchy that can be dispersed throughout my Views?

Right now I have a rather large ViewModel called MainViewModel, that contains a lot of commands and properties that could be organized into more reasonably named ViewModels.

I however, only have one window, and so need to be able to cherry-pick the valid data and Commands from each of the SubViewModels....

I figure this could be achieved using properties, but I'm not so sure how to approach this in the XAML. (Or if there is an implication in the ViewModels themselves)

I realize that I can set the DataContext on SubViews as I see fit, but I want to avoid having my View dictate the hierarchy/organization of my ViewModels.

Ex. pseudo code 

SubAViewModel mvmB = new SubBViewModel();
SubAViewModel mvmA = new SubAViewModel();
MainViewModel mvm = new MainViewModel( mvmA, mvmB );

<Window DataContext="{StaticResource MainViewModel}">

    //This is clearly wrong but is sort of what I am trying to achieve
    <MenuItem Command="{Binding Path=MainViewModel.SubAVM.TargetCmd}" />

It's entirely possible that a MenuItem or some other UserControl would want to access a Command in SubBViewModel and a property in SubAViewModel.

Upvotes: 0

Views: 775

Answers (1)

Raffaeu
Raffaeu

Reputation: 6973

If you set the data context of the View to the MainViewModel and you expose the SubAVM as a property like this one:

public SubViewModel SubAVM { 
   get { 
      return subAVM;
   }
   set{
   if (subAVM == value)
   {
      return;
   }
   subAVM = value; //implement the OnPropertyChanged ...
   }
}

Of course the Path on a MenuItem would be SubAVM.TargetCmd as by the dependency hierarchy the main path is already MainViewModel for a Menu.

Upvotes: 3

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