COM & .NET Component Services

Definitions and Text Conventions

The following definitions and conventions apply throughout this book:

• A component is an implementation of a set of interfaces. A component is what you mark in your IDL file (or type library) with CoClass or a class in C#.

• An object is an instance of a component. You can create objects by calling CoCreateInstance( ) in C++, specifying the class ID (the type) of the object you want to create. If you use Visual Basic 6.0, you can create objects using new or CreateObject( ). A C# client uses new to create a new instance of a component.

• I use the following terms in the book: CoCreating refers to calling CoCreateInstance() in C++, or new or CreateObject( ) in Visual Basic. Querying an object for an interface refers to calling IUnknown::QueryInterface( ) on the object. Releasing an object refers to calling IUnknown::Release( ) on the object.

• The graphical notations in Figure P-1 are used in almost every design diagram in the book. The “lollipop” denotes an interface, and a method call on an interface is represented by an arrow beginning with a full circle.

Figure 1. Interface and method call graphical notations

• Error handling in the code samples is rudimentary. The code samples serve to demonstrate a design or a technical point, and cluttering them with too much error handing would miss the point. In a production environment, you should verify the returned ...