The closest I could find to this question was this one: Getting all types that implement an interface
But that is for use in code, and to use it I\'d have to change
No there's not an easier way. I guess that way is pretty easy to do. It's just three lines. You can cache the results in a list or dictionary (in case you want to test it for a collection of interfaces) if you need to do it many times in a row.
In case you need just as a tool, Reflector does it.
Using ReSharper, right-click on the Interface, go to Implementation, choose the one you want to see from the list it populates.
I don't think there's a way to do it programatically, but if you just mean in the IDE, this is the easiest way to do so.