Summary

This chapter provided a detailed view of the type system of the Common Language Runtime. The CLR supports an object-oriented programming style, which is reflected in its type system. The CTS contains two basic types: value types and reference types. Value types are similar to primitive types in many programming languages. Reference types are analogous to classes in many object-oriented languages; they are further divided into object, interface, and pointer types.

All object types inherit from Object. Object types may introduce new methods, these methods can be either static or instance; instance methods can also be virtually dispatched. Methods may, of course, follow the rules for properties or events, thereby gaining additional support from the CLR or other tools.

Methods may be overloaded. In other words, a class can have many methods with the same name as long as the types of the methods' parameters are different. When a program calls a method with multiple names, the choice of which method is called depends on the argument list and its correspondence with the available methods' signatures.

Virtual methods may also be overridden. In such a case, subtypes supply methods with exactly the same signatures as the base classes. The compiler may issue instructions to do runtime dispatching of the method call. The method selection is then left until runtime, when the exact type of the object on which the method acts is known.