VB Shell Programming

Type Libraries

The interface and co-class definitions are stored in a special file called a type library. In the case of Animals.dll, VB creates the type library automatically and stores it as a resource inside the component. But you can also create your own type libraries. The type libraries that you create can then be referenced from VB. In fact, since VB does not allow us to create type information that is suitable for our needs in developing shell extensions, we’re going to have to create our own type library. But before we do that, we will talk about what a type library is and what goes inside of one.

A type library is a language-independent binary file that contains all the information needed to use the component. This includes interface definitions, co-class definitions, structures (UDTs), enumerations, and constants. It is because of type libraries that Visual Basic can implement such great features as Auto List Members (shown in Figure 2.4), Auto Quick Info, and the Object Browser.

Figure 2-4. Auto List Members from type library

Object Browser is really just a simple type library browser. Although it can provide some very useful information, it does hide a number of things that Microsoft does not want VB programmers to know about. Fortunately, there is a utility called the OLE/COM Object Viewer (usually referred to as OLE View) that will allow us to view the type library generated ...