How to reference a generic type in the DataType attribute of a HierarchicalDataTemplate?

Question

I have a class of MyClass and want to set it as the DataType for a HierarchicalDataTemplate.

What is the syntax for this in XAML? (I kno

Answer 1

This is not supported in WPF 3.x out of the box (I think it may be in 4.0, but I'm not sure); but it's easy to set up with a markup extension.

First, you need to create a markup extension class that takes the type parameter as a constructor argument:

public class MyClassOf : MarkupExtension
{
  private readonly Type _of;

  public MyClassOf(Type of)
  {
    _of = of;
  }

  public override object ProvideValue(IServiceProvider serviceProvider)
  {
    return typeof(MyClass<>).MakeGenericType(_of);
  }
}

Now you use this markup extension in place of the x:Type extension:

Needless to say, this can be generalised to allow instantiation of arbitrary generic types; I haven't shown this because it adds a wee bit more complexity.