C# Language Pocket Reference

Structs

A struct is similar to a class, with the following major differences:

• A class is a reference type, while a struct is a value type. Consequently, structs are typically used to express simple types, in which value-type semantics are desirable (e.g., an assignment copies a value rather than a reference).

• A class fully supports inheritance, whereas a struct can inherit only from an object and is implicitly sealed (in the runtime, structs actually inherit from System.ValueType). Both classes and structs can implement interfaces.

• A class can have a destructor, and a struct cannot.

• A class can define a custom parameterless constructor and initialize instance fields, while a struct cannot. The default parameterless constructor for a struct initializes each field with a default value (effectively zero). If a struct declares a constructor(s), then all of its fields must be assigned in that constructor call.

Here is a simple struct declaration:

struct Point {
  public int x, y;
}

To create a struct, you can use the new operator, which will initialize all the struct members to their defaults (zero in the case of x and y). If you do not use the new operator, you will need to initialize the struct members yourself. You can also use array declaration syntax to create an array of structs:

Point p1 = new Point(  );
Point p2;
p2.x = p2.y = 0;
Point[] points = new Point[3];