Here is a trick you could use.

1. Make sure your Silverlight Views and View Models are isolated within their own assembly that is easily referenceable by your WPF application.
2. Add a reference to the Silverlight class library that houses the Views & View Models in the WPF application.
3. Move the contents of the UserControl, “CustomerView” into a DataTemplate housed in a resource dictionary called “customerViewTemplate”
4. Inside your root UI element XAML files in Silverlight and WPF do this:

<ContentControl ContentTemplate="{Staticresource customerViewTemplate}" />

1. In the Silverlight application’s App.xaml make sure to add the following Resource Dictionary reference to the merged dictionaries.

<ResourceDictionary Source="MyApp.Views;component/CustomerViewResources.xaml" />

1. In the WPF application’s App.xaml make sure to add the following resource dictionary reference to the merged dictionaries.

<ResourceDictionary Source="pack://application:,,,/MyApp.Views;component/CustomerViewResources.xaml" />

Sorry about the numbering, looks like Stack Overflow’s ordered list mechanism is a little off.

The reason why this works is because you can’t directly reference a Silverlight UserControl from XAML within WPF. It will give you the following error:

‘Cannot resolve dependency to assembly ‘System.Windows, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e’ because it has not been preloaded. When using the ReflectionOnly APIs, dependent assemblies must be pre-loaded or loaded on demand through the ReflectionOnlyAssemblyResolve event.

If you try to force the UserControl onto a WPF Grid using C# you will get the following 3 errors:

The best overloaded method match for ‘System.Windows.Controls.UIElementCollection.Add(System.Windows.UIElement)’ has some invalid arguments.

The type ‘System.Windows.Controls.UserControl’ is defined in an assembly that is not referenced. You must add a reference to assembly ‘System.Windows, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e’

cannot convert from ‘ToWpfTest.Views.TestView’ to ‘System.Windows.UIElement’

I gather this is because the System.Windows.UIElement in WPF is not the same as the System.Windows.UIElement in Silverlight.

Here is a screen shot of the Silverlight Class Library being referenced directly by the WPF application.

Here is a sample solution.