New Post: Action.Target string

In the docs, it states the following about using a string value in an Action.Target:

Action.Target– Sets both the Action.Target property and the DataContext property to the specified instance. String values are used to resolve an instance from the IoC container.

I am trying to get this to work but can't find a sample of it.  For example:

<Button cal:Action.Target="TestClass"
                cal:Message.Attach="TestMethod"
                Content="Click Me">

In other words, in my bootstrapper, I add an instance of TestClass and I want to be able to call TestMethod on it.

Greg