One of the features introduced with Visual Studio 2005 was the capability to generate class diagrams. A class diagram is a graphical representation of your application's objects. By right-clicking on your project in the Solution Explorer, you can select View Class Diagram from the context menu. Alternatively, you can choose to Add a New Item to your project. In the same window where you can add a new class, you have the option to add a new class diagram. The class diagram uses a .cd file extension for its source files. It is a graphical display, as shown in Figure 1-42.
Adding such a file to your project creates a dynamically updated representation of your project's classes. As shown in Figure 1-42, the current class structures for even a simple project are immediately represented when you create the diagram. It is possible to add multiple class diagrams to your project. The class diagram graphically displays the relationships between objects — for example, when one object contains another object or even object inheritance. When you change your source code the diagram is also updated. In other words, the diagram isn't something static that you create once at the start of your project and then becomes out-of-date as your actual implementation changes the class relationships.
More important, you can at any time open the class diagram, make changes to one or more of your existing objects, or create new objects and define their relationship to your existing objects, and when done, Visual Studio will automatically update your existing source files and create new source files as necessary for the newly defined objects.
As shown in Figure 1-42, the class diagram files (*.cd) open in the same main display area used for the Visual Studio UI designer and viewing code. They are, however, a graphical design surface that behaves more like Visio than the User Interface designer. You can compress individual objects or expose their property and method details. Additionally, items such as the relationships between classes can be shown graphically instead of being represented as properties.
In addition to the editing surface, when working with the Class Designer a second window is displayed. As shown at the bottom of Figure 1-42, the Class Details window is generally located in the same space as your Output, Tasks, and other windows. The Class Details window provides detailed information about each of the properties and methods of the classes you are working with in the Class Designer. You can add and edit methods, properties, fields, and even events associated with your classes. While you can't write code from this window, you can update parameter lists and property types. The Class Diagram tool is an excellent tool for reviewing your application structure.
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