What about Structs?
By Dino Karatzios

A new feature that was introduced in the C# language is the STRUCT object. To give a general and easy definition of STRUCTS, you can think of them as something like a scaled down class. One important aspect of STRUCTS is that they were designed for situations where you simply wanted to group data that is relative.

Example of Class vs. Struct ’

class Teacher { private string Name; private string Address; private string City; private long Phone; }

struct Teacher { private string Name; private string Address; private string City; private long Phone; }

So, why use a struct and not a class object? Before answering that question, we should look at the significant differences between both objects. First and foremost, a STRUCT is a value-type object, while class is a reference type object. If you are not familiar with value-type and reference type objects, this simply means that the STRUCT object is allocated (stored) in a location of memory called the stack, and the class object is allocated (stored) in another section of memory called the heap.

Allocating memory for a STRUCT object on the stack does have it’s advantage. Because it is on the stack, retrieving data from the STRUCT’s members is very fast, as is removing them from the stack. The disadvantage however, is that when a struct object is assigned to another struct object (see below), the full content of the struct that is being copied is duplicated and added to the stack, resulting in a lost efficiency known as a performance hit. When using a reference type object however, only a reference to the class is added to the stack.

Example using a class public void SomeMethodB() { Teacher A = new Teacher(); Teacher B = A; } * Note: class A and class B are both referencing the same object on the heap. Only a new reference has been added to the stack.

Example using a struct public void SomeMethodA() { Teacher A = new Teacher(); Teacher B = A; } * Note: struct A and struct B are both allocated in the stack even though they contain the same members.

Structs and Inheritance?

The second significant difference between class objects and struct objects is about inheritance. Let us cut the chase and get right to the point, structs do no support inheritance. This means that it is not possible to inherit a struct , nor can a struk be derived from.

Structs and Constructors?

The third significant difference between class objects and struct objects refers to constructors. Constructors are supported by structs in the C# language, and you can define constructors for structs in exactly the same manner as you would for classes. If you are not familiar with constructors, they are methods with the same name as the struct or class ( see figure below). However, the only exception with struct constructors is that you are not permitted to define a constructor that takes no arguments.

Example of a valid constructor

using System;

struct Teacher
{
 private string Name;
 private string Address;
 private string City;
 private long Phone;

 //Structs' Constructor
 public Teacher(string name, string address, string city, string phone) 
 {
  Name = name;
  Address = address;
  City = city;
  Phone = phone;
 }
}

using System;

struct Teacher
{
 private string Name;
 private string Address;
 private string City;
 private long Phone;

//Structs\’ Constructor is not valid because there are no
//arguments defined. A constructor with no arguments is not permitted!.
 public Teacher() 
 {
  Name = "Bob" ;
  Address = "50 King St.";
  City = "Saint John";
  Phone = 643-2333;
 }
}

using System;

struct Grade
{
 int x;
 int y;

 public ShowValues()
 {
  Console.WriteLine("x is {0}", x); 
  Console.WriteLine("y is {0}",y);
 } 
}

class Test
{
 public static void Main()
 {
  //When we instantiated the struct Grade using the new operator,
  //the default constructor will run and assign the values 0 for x
  //and 0 for y. This is why the answer will be:
  //x is 0
  //y is 0
  Grade g = new Grade();
  g.ShowValues()
 }
}

Grade g;
g.ShowValues();