Question

enter code hereMaybe the title is not so specific.

The situation which I’m having is. I’ve got an ItemsControl where I insert many ViewModels, and this ItemsControl should have to show the View through DataTemplates.

So, I write these in a ResourceDictionary:

And then, I add this ResourceDictionary to the ApplicationResources.

This is so redundant and tiredsome.

I’m using MVVM also, so I was thinking if could be a way to use MEF to discover the corresponding the View that should draw. I was investigating that creating a custom attribute tag could be a good idea to simplify these redundant code, maybe adding this tag in the view telling it that this ViewModel should draw for this View, but I get lost with MEF.

The plan is to remove the ResourceDictionary.

Can you lend me a little hand?

Thanks in advance.

Answer 1

[System.ComponentModel.Composition.InheritedExport(typeof(ProblemView))]
public abstract class ProblemView : UserControl // or whatever your Views inherit
{
   public abstract Type ViewModelType { get; }
}

[System.ComponentModel.Composition.InheritedExport(typeof(ProblemViewModel))]
public abstract class ProblemViewModel : BaseViewModel // or whatever your ViewModels inherit
{
}

// in your App class
{
   [ImportMany(typeof(ProblemView))]
   public ProblemView[] Views { get; set; }
   [ImportMany(typeof(ProblemViewModel))]
   public ProblemViewModel[] ViewModels { get; set; }

   void MarryViewViewModels()
   {// called during MEF composition
      foreach (ProblemView view in Views)
      {
         foreach(ProblemViewModel vm in ViewModels)
         {
            if(Equals(view.ViewModelType, vm.GetType())
            {// match -> inject the ViewModel
               view.DataContext = vm;
               break;
            }
         }      
      }
   }
}

// example of usage
public partial class SomeView : ProblemView
{
   public override Type ViewModelType { get { return typeof(SomeViewModel); } }
}