VB.NET Language in a Nutshell, Second Edition

Chapter 7. Delegates and Events

In this chapter, we discuss delegates and events, two additional .NET framework topics that are important to VB programmers.

Delegates

In a never-ending effort to deny VB programmers the right to use pointers, Microsoft has implemented a feature called delegates that, according to the documentation, provide a safe alternative to function pointers.

As you may know, a pointer variable (or pointer) is simply a variable whose value is interpreted by the compiler as a memory address. The address to which the pointer points is the target of the pointer, and we say that the pointer variable points to that target address. If the target address is a variable of data type Integer, for example, then we say that the pointer is of type Integer or is an Integer pointer. Thus, the type of a pointer is the type of the target variable. (We have seen that, as reference types, variables of type Object and String are both pointers; i.e., their values point to the address of the data in memory.)

A pointer can also point to a function, that is, contain the address of a function. Even though a function is not a variable, it does have a physical location in memory and so can be the target of a pointer. (Actually, it’s reasonable to think of a function as a type of variable, but that is another story.) In this case, we have a function pointer.

Function pointers are very useful in certain situations for calling or specifying functions. This is commonly done in the C++ programming ...