Chapter 3. Classes and Structures

3.0. Introduction

Structures, like any other value type, implicitly inherit from System.ValueType. At first glance, a structure is similar to a class, but it is actually very different. Knowing when to use a structure over a class will help tremendously when designing an application. Using a structure incorrectly can result in inefficient and hard-to-modify code.

Structures have two performance advantages over reference types. First, if a structure is allocated on the stack (i.e., it is not contained within a reference type), access to the structure and its data is somewhat faster than access to a reference type on the heap. Reference-type objects must follow their reference onto the heap in order to get at their data. However, this performance advantage pales in comparison to the second performance advantage of structures; namely, that cleaning up the memory allocated to a structure on the stack requires a simple change of the address to which the stack pointer points, which is done at the return of a method call. This call is extremely fast compared to allowing the garbage collector to automatically clean up reference types for you in the managed heap; however, the cost of the garbage collector is deferred so that it's not immediately noticeable.

The performance of structures falls short in comparison to that of classes when they are passed by value to other methods. Because they reside on the stack, a structure and its data have to be copied to ...

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