7.6. Summary

Hooray—you did it! You made it through all of the major OO technology concepts that you'll need to know for the rest of the book, learning a great deal of C# syntax in the process.

Please make sure that you're comfortable with these concepts before proceeding to Part Two because they will form the foundation of the rest of your object learning experience:

• These same concepts will be reinforced when you learn how to model a problem in Part Two.

• They will be reinforced yet again when you learn how to render a model as C# code in Part Three.

In this chapter, you learned the following:

• Different objects can respond to the same exact method call in different class-specific ways, thanks to an OOPL feature known as polymorphism.

• Abstract classes are useful if we want to prescribe common behaviors among a group of (derived) classes. We specify the "what" that an object must do (the messages that an object must be able to respond to, also known as method signatures) without specifying the "how" (the method bodies) in the base class.

• Interfaces are an even more abstract way to prescribe behaviors; in essence, interfaces define roles that objects can play.

• Static fields/properties can be used to enable an entire class of objects to share data, and static methods enable us to provide capabilities that are available to the application through a class as a whole.

• How to take advantage of static members along with constant fields to create custom utility classes.

The first part of this book has given you all the programming tools you'll need in your toolbox to build powerful C# applications. But you still need to learn how to lay out a blueprint for using them effectively in building an application—we'll teach you how to do so in Part Two!