Set d:DataContext to an internal class of another assembly

Question

Consider the following scenario:

WPF view:

d:DataContext="{d:DesignInstance vm:DesignViewModel, IsDesignTimeCreatable=True}"

ViewModel is located in a separate c# project:

internal class DesignViewModel : ViewModel 
{ /* create demo data in ctor */ }

ViewModel has this entry in AssemblyInfo:

[assembly: InternalsVisibleTo("WPF.Demo.View")]

Error message in XAML Designer:

• The name "DesignViewModel" does not exist in the namespace "WPF.Demo.View".

Observations:

• Everything works fine if I make DesignViewModel public, instead of internal. But, I'd like to keep it internal, for external consumers really shouldn't bother about design time stuff.
• Everything works fine if I move DesignViewModel into the same assembly that holds the view. But, I'd like to keep view and ViewModel separate.
• InternalsVisibleTo is set correctly, for I can access it from code behind in the view.

Question: How can I set d:DataContext to an internal class of another assembly?

Answer 1

You can't. By definition, when you mark an artifact as internal you are making it invisible from other assemblies.

Alternatively, you can expose a method on a public object, that makes what you want in the assembly's objects.

Regards,