Classes In C#

Class is consists of data and behavior. Class data is represented by it's fields and behavior is represented by its methods. 

Example:

class Customer

    {

        string first_Name;

        string last_Name;

        //Default parameterless constructor

        public Customer() : this("No FirstName Provided", "No LastName Provided")

        {

        }

        public Customer(string f_Name,string l_Name)

        {

            this.first_Name = f_Name;

            this.last_Name = l_Name;

        }

        public void printFullName()

        {

            Console.WriteLine("Full Name = {0}" ,this.first_Name+" "+this.last_Name);

        }

        ~Customer()//destructor call automatically

        {

            //Clean up code

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            Customer C1 = new Customer("Brij","Pal"); //here constructor used to initializing the member of class

            C1.printFullName();

            Customer C2 = new Customer(); //Here called the default constructor

            C2.printFullName();

            Console.ReadLine();

        }

       

    }

Purpose of Constructors:

• The purpose of a class constructor is to initialize class fields. A class constructor is automatically called when an instance of class is created.
• Constructor do not have a return values and always have the same name as the class name.
• Constructors are not mandatory. if we do not provide a constructor, a default parameter less constructor is automatically provided.
• Constructors can be overloaded by the number and type of parameters. 

Destructors:

1. Destructors have the same name as the class with ~symbol in front of them.
2. They don't take any parameters and do not return a value.
3. Destructors are places where you could put code to release any resources your class was holding during lifetime.
4. They are normally called when the C# garbage collector decides to clean your object from memory.