d:DesignInstance with an interface type
I'm binding an UI to an interface (which is implemented by several presenters, not accessible from the UI assembly). I really like d:DesignInstance in designer because it (kind of) makes xaml strongly typed using R#. Sadly, d:DesignInstance does not support interface types: "Cannot create an instance of an interface." The first thing I thought is: Ok, no problem, let's create a custom markup extension which takes a System.Type as parameter, and which ProvideValue method returns a fake instance of it (dummy implementation of this interface, generated by dynamic IL emission). This works quite