Get all inherited classes of an abstract class - Editor Scripting

This question and answer: http://stackoverflow.com/questions/5411694/get-all-inherited-classes-of-an-abstract-class

Except that, apparently, the "Assembly" object doesn't exist in the context of the UnityEditor.

Ideas?

Usage: Working on a custom Event Handler with user defined behaviors, and in the Custom Inspector when you hit "Add Behavior" I want to pop a list of possible behaviors, but I don't want to have some kind of actual list anywhere - ideally, you only have to define the new behavior (and inherit from the Behavior abstract class), and everything is taken care of.

Update:

Via Jordan's answer below, here's the working, compact version `using System.Linq` and `using System.Reflection`:

 System.Type[] types = System.Reflection.Assembly.GetExecutingAssembly().GetTypes();
 System.Type[] possible = (from System.Type type in types where type.IsSubclassOf(typeof(BaseClass)) select type).ToArray();