Here is how to refactor (or at least how I refactor, there are other ways) this example I posted earlier.  The class Foo can pretty much be implemented however you want.  In my case, I wanted to get the number of required tokens for a specific person using an interface.  You can see that I created in interface IPerson that contains GetNumberOfRequiredTokens.  This way I can just pass in an IPerson object type and use the polymorphed, overriden function in the child class, or adult class (each of which inherit from the Person class that implements the IPerson interface).  I implemented a property in the base class that contains the default number of tokens, and then for each derived class, I use that along with custom calculations the derived class to come up with the appropriate number of tokens required.

The refactoring pattern we are targeting here is called “conditional to polymorphism”, along with a few other names.  The goal was to refactor our initial “Select Case” into a base class with derived classes.  This increases usability and scalability greatly over our initial code we started with.

Don’t forget, and I did not demonstrate this, you will ALWAYS want to write a unit test for your initial code (Foo.GetNumberOfRequiredTokens) and make sure it passes all scenarios BEFORE beginning your refactoring process and DURING and AFTER your refactoring process.

To test this, create a new object of type Adult.  Then call Foo.GetNumberOfRequiredTokens(adultObject) and it will return 3.