Struct in C#

A struct type is a value type that is typically used to encapsulate small groups of related variables, such as the coordinates of a rectangle or the characteristics of an item in an inventory. The following example shows a simple struct declaration:

 

public struct Book {     public decimal price;     public string title;     public string author; }

 

 

Structs can also contain constructors, constants, fields, methods, properties, indexers, operators, events, and nested types, although if several such members are required, you should consider making your type a class instead.

Structs can implement an interface but they cannot inherit from another struct. For that reason, struct members cannot be declared as protected.

                                                                                                                                   

 

Using Struct

The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is just as convenient to represent a point as a class with Auto-Implemented Properties, a struct might be more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object; in this case, a struct would be less expensive. Because the .NET Framework contains an object called Point, the struct in this example is named "CoOrds" instead.

 

public struct CoOrds {     public int x, y;       public CoOrds(int p1, int p2)     {         x = p1;         y = p2;     } }

 

 

It is an error to define a default (parameterless) constructor for a struct. It is also an error to initialize an instance field in a struct body. You can initialize struct members only by using a parameterized constructor or by accessing the members individually after the struct is declared. Any private or otherwise inaccessible members can be initialized only in a constructor.

 

When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. In such a case, there is no constructor call, which makes the allocation more efficient. However, the fields will remain unassigned and the object cannot be used until all of the fields are initialized.

 

There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.

You cannot declare a class using the keyword struct. In C#, classes and structs are semantically different. A struct is a value type, while a class is a reference type.

 

Unless you need reference-type semantics, a small class may be more efficiently handled by the system if you declare it as a struct instead.