Constructor and Destructor in C#

Nov 20, 2018 / by Kamlesh Bhor / Views

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Constructor:

It is used to initialize the variables in the class and used to create object for the class in memory.

Features Of Constructor:

Constructor name & class name will be same.
Constructor will be declared as public so that it can be called or executed in main function.
Constructor will not have return type & will not return value.
Constructor can contain arguments. It is called parameterized constructor.
A class can contain more than one constructor. It is called as constructor overloading. A class can contain more than one constructor but there should be difference in a number of arguments or order of arguments or difference in datatypes.
Default constructor means if the class is not containing constructor then compiler will use default constructor while creating object for the class. Default constructor will never take arguments.
Private constructor can be accessed within the class. It can be executed with public constructor.
Static constructor is used to initialize the static variables in a class.

Examples:

1) Constructor containing two arguments:

using System;

namespace Demo
{
    class clsEmp
    {
        public int eno;
        public string ename;
        public clsEmp(int eno,string ename) //Creating constructor
        {
            this.eno = eno;
            this.ename = ename;
        }
        public void getdetails()
        {
         Console.WriteLine(eno + " " + ename);
        }
    }
    class Demo
    {
        static void Main(string[] args)
        {
            clsEmp obj = new clsEmp(101, "Kamlesh"); //calling constructor
            obj.getdetails();
            Console.Read();
        }
    }
}

Output:

Note:

'This' represents current class. It is a predefined object in c# used to work with variables in current class.

2) Constructor containing one string argument:

using System;

namespace Demo
{
    class clsinfo
    {
        public string s;
        public clsinfo(string s)
        {
            this.s = s;
        }
        public void getstring()
        {
         Console.WriteLine(s);
        }
    }
    class Demo
    {
        static void Main(string[] args)
        {
            clsinfo obj = new clsinfo("Kamlesh");
            obj.getstring();
            Console.Read();
        }
    }
}

Output:

3) Constructor containing private & public constructor:

using System;

namespace Demo
{
    class clsinfo
    {
        public string s;
        private clsinfo()
        {
            Console.WriteLine("Ms.Net");
        }
        public clsinfo(string s):this()
        {
            this.s = s;
        }
        public void getstring()
        {
            Console.WriteLine(s);
        }
    }
    class Demo
    {
        static void Main(string[] args)
        {
            clsinfo obj=new clsinfo("VC#4.5");
            obj.getstring();
            Console.Read();
        }
    }
}

Output:

4) Constructor containing two public constructor:

namespace Demo
{
    class clsemp
    {
        public int eno;
        public string ename;
        public clsemp()
        {
            eno=999;
            ename="Kamlesh";
            Console.WriteLine(eno+" "+ename);
        }
        public clsemp(int eno,string ename)
        {
            this.eno = eno;
            this.ename = ename;
        }
        public void getdetails()
        {
            Console.WriteLine(eno + " " + ename);
        }
    }
    class Demo
    {
        static void Main(string[] args)
        {
            clsemp obj1 = new clsemp();
            clsemp obj2 = new clsemp(888, "Bhor");
            obj2.getdetails();
            Console.Read();
        }
    }
}

Output:

5) Using static constructor:

using System;

namespace Demo
{
    class abc
    {
        public static int a;
       static abc()
       {
            a=100;
        }
        public static void getA()
        {
            Console.WriteLine(a);
        }
    }
        
    class Demo
    {
        static void Main(string[] args)
        {
            abc.getA();
            Console.Read();
        }
    }
}

Output:

Destructor:

Destructor is used to delete object from memory.

Features Of Destructor:

Destructor name & class name will be same.
Destructor will start with (~) tilde symbol.
Destructor will not have return type & will not return value.
Destructor will not take arguments.
A class can contain only one destructor.

Example of destructor:

using System;
namespace Demo11
{
    class Demo
    {
        // Constructor
        public Demo()
        {
            Console.WriteLine("An  Instance  Created");
        }
        // Destructor
        ~Demo()
        {
            Console.WriteLine("An  Instance  Destroyed");
        }
    }

    class Program
    {
        public static void Test()
        {
            Demo T = new Demo(); // Created instance of class
        }
        static void Main(string[] args)
        {
            Test();
            GC.Collect();
            Console.ReadLine();
        }
    }
}

Output:

Note:

Constructor is executed when program execution is started. Destructor will execute before the program execution will end. Constructor will be called in main() & destructor will be called by the compiler. To get the same result window again press ctrl+f5. To delete unreferenced objects from heap memory, System.GC.Collect() should be used.

In this way, we have learned Constructor and destructor with examples in this article. I hope this will help beginners to understand Constructor and destructor.

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Constructor and Destructor in C#

Constructor:

Features Of Constructor:

Examples:

1) Constructor containing two arguments:

Output:

Note:

2) Constructor containing one string argument:

Output:

3) Constructor containing private & public constructor:

Output:

4) Constructor containing two public constructor:

Output:

5) Using static constructor:

Output:

Destructor:

Features Of Destructor:

Example of destructor:

Output:

Note:

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