Structures (keyword struct) are light-weight objects. They are mostly used when only a data container is required for a collection of value type variables. Structs are similar to classes in that they can have constructors, methods, and even implement interfaces, but there are important differences. Structs are value types while classes are reference types, which means they behave differently when passed into methods as parameters. Another very important difference is that structs cannot support inheritance. While structs may appear to be limited with their use, they require less memory and can be less expensive if used in the proper way.

A struct can, for example, be declared like this:

struct Person
{
    string name;
    System.DateTime birthDate;
    int heightInCm;
    int weightInKg;
}
                                          

The Person struct can then be used like this:

Person dana = new Person();
dana.name = "Dana Developer";
dana.birthDate = new DateTime(1974, 7, 18);
dana.heightInCm = 178;
dana.weightInKg = 50;

if (dana.birthDate < DateTime.Now)
{
    Console.WriteLine("Thank goodness! Dana Developer isn't from the future!");
}
                                          

It is also possible to provide constructors to structs to make it easier to initialize them:

using System;
struct Person
{
    string name;
    DateTime birthDate;
    int heightInCm;
    int weightInKg;

    public Person(string name, DateTime birthDate, int heightInCm, int weightInKg)
    {
        this.name = name;
        this.birthDate = birthDate;
        this.heightInCm = heightInCm;
        this.weightInKg = weightInKg;
    }
}

public class StructWikiBookSample
{
    public static void Main()
    {
        Person dana = new Person("Dana Developer", new DateTime(1974, 7, 18), 178, 50);
    }
}
                                          

All text is available under the terms of the GNU Free Documentation License
Source : Wikibooks