VB Shell Programming

Conclusion

You should have a basic understanding of the components you are creating with Visual Basic. This chapter, far from being a comprehensive treatise on COM, is merely meant to introduce some of the fundamental concepts that we will be dealing with throughout the remainder of this book. It does not represent the extent of the book. Many new concepts will be discussed as the need arises. For now, you should have a basic understanding of COM, the architecture used by Visual Basic for creating component-based software. These components expose their functionality through interfaces. Interface definitions are stored in a type library, which provides information to clients that wish to use the object. Interface definitions are written in IDL, which is the standard language for defining interfaces, and compiled with the MIDL compiler or MKTYPLIB. The fundamental interface that all objects have in common is IUnknown. IUnknown contains methods that allow for interface discovery and reference counting. The interfaces of objects created with Visual Basic are derived from IDispatch, making the process of runtime binding possible.