Question

I’ve got a WPF MVVM application. One of my views has a user control that needs to be customizable for each installation. It’s basically a sketch of the customers installation with some labels etc. bound to a viewmodel.

Now my problem is that this user control is different on each site/installation. One approach is to load the xaml from a file/database runtime using a xaml reader. This works but since my viewmodel is generic I have to bind to methods instead of properties and I can’t load a xaml with objectdataprovider.

Currently I’m trying to see if MEF can be used so that I can create the user control as a plug-in. So what I’m looking for now is this:

1. how can I define a user control with view/view model that exports a contract for MEF
2. How can my parent view (in my wpf app) load the imported user control

Any tips are appreciated, or maybe someone has a different approach?

Answer 1

I suggest you look into Prism in combination with MEF. It has a notion of Modules (plug-ins in your case) and Regions (mechanism of dynamically loading views).

You will be able to export a view using a simple attribute:

[ViewExport(RegionName = RegionNames.MyRegion)]
public partial class MyView : UserControl {
    public MyView() {
        this.InitializeComponent();
    }

    [Import]
    public MyViewModel ViewModel {
        set { DataContext = value; }
    }
}

[Export]
public class MyViewModel : ViewModelBase
[
  ...
}

And in your main application XAML you will be able to import the plugin’s views like this:

<ContentControl Regions:RegionManager.RegionName="{x:Static Infrastructure:RegionNames.MyRegion}"/>