Constructors and Destructors in C#.Net

Ramakrishna Basagalla

4y182.5k10100Article

C#.NET ConstructorsDestructorsConstructors Destructors C#.Net

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Abhishek Jaiswal12y ago
Nicely Explained!
Sam Hobbs14y ago
Destructors are usually not needed, correct? I think the first thing that should be said about Destructors is that they are usually not needed. The most common use of destructors is to do cleanup of unmanaged objects.
- Vijay Gill14y ago
  @Sam: relying on destructors to clean up unmanaged resources is not a good idea because calling of destructors is dependent on GC (http://msdn.microsoft.com/en-us/library/66x5fx1b.aspx). Better way to deal with that is implementation of IDisposable interface (which when used with 'using' statement) for releasing unmanaged resources deterministic way. Vijay
- Vijay Gill14y ago
  @Sam: I hope this does not start a flamewar which I never intend to. But developing good coding habits right from the beginning is very important. In C# IDisposable is a pattern that C# developers use in the same way as C++ developers use destructors. It is used in .Net framework itself for a lot of classes. IDisposable pattern, though a bit complex, is not rocket science and beginners can always start with the simplest approach and improve their knowledge+code as they go on. The main benefit of IDisposble is 'deterministic nature' of its usage.
- Sam Hobbs14y agoedited
  Vijay and others, the important thing is that the subjects of destructors and IDisposable is complex. The important thing is that most managed code does not need any of it. Saying that we need IDisposable instead of destructors makes things more confusing. Can someone please make it clear that a beginner can ignore this stuff until they learn more? A C# beginner that is experienced with C++ can get really confused about this stuff and usually they don't need it.
Vineet Kumar Saini15y ago
Very useful for beginner student.......
Vineet Kumar Saini15y ago
Very useful for beginner student.......
ashish f15y ago
Can we override constructor???
- Vijay Gill15y ago
  Default constructors cannot be overridden. Non-default constructor are automatically overridden (unless you call base constructor also).
Vijay Gill15y ago
this is a test Another line

Constructor

Constructors are special methods called when a class is instantiated.

Constructor will not return anything.
Constructor name is same as class name.
By default C# will create default constructor internally.
Constructor with no arguments and no body is called default constructor.
Constructor with arguments is called parameterized constructor.
Constructor by default public.
We can create private constructors.
A method with same name as class name is called constructor there is no separate keyword.

Sample Program

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BRK.ConstructorExample
{
    class Welcome
    {
        // Default constructor
        public Welcome()
        {
            Console.WriteLine("Welcome message from Default Constructor...");
        }

        // Parametarized constructor
        public Welcome(string name)
        {
            Console.WriteLine("\n\nThis message from parametarized constructor");
            Console.WriteLine("Welcome to Constructor sample, by {0}", name);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            // Creating object for Welcome class
            // This will called default constructor
            Welcome obj = new Welcome();

            // Creating object for welcome class by passing parameter
            // This will called parametarized constructor which matches
            Welcome pObj = new Welcome("Ramakrishna Basgalla");

            Console.Read();
        }
    }
}

Output

Private Constructor

As I mentioned above we can create private constructors, but we have limitation in using that. The following program shows how to create and use a private constructor.

Sample Program

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BRK.PrivateConstructorSample
{
    class Welcome
    {
        // Default private constructor
        private Welcome()
        {
            Console.WriteLine("Welcome message from Default Private Constructor...");
            Console.WriteLine("Created by Ramakrishna Basagalla (-:");
        }

        static void Main(string[] args)
        {
            // Creating object for Welcome class
            // This will called default private constructor
            Welcome obj = new Welcome();

            Console.Read();
        }
    }
}

Output

To use a private constructor we should have main function in the same class, generally we will define constructors in different classes so defining private constructors is not that much useful.

Static Constructor

A static constructor has the same name as the class name but preceded with the static keyword; it will be called at the time of class load.

No access specifier for static constructor.
Static constructor will not return anything.
Static constructor will accept only static members.
Static constructor will call at the time of class loading.
Static constructor will not allow overloading, so there is no parameterized static constructor.

Sample Program

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BRK.ConstructorExample
{
    class Welcome
    {
        public static string Name = "Ramakrishna Basagalla";

        // Static Constructor
        static Welcome()
        {
            Console.WriteLine("Welcome message from static Constructor...");
            Console.WriteLine("{0} name is coming from static member",Name);
        }

        // Parametarized constructor
        public Welcome(string name)
        {
            Console.WriteLine("\n\nThis message from parametarized constructor");
            Console.WriteLine("Welcome to Constructor sample, by {0}", name);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            // Creating object for welcome class by passing parameter
            // This will called parametarized constructor which matches
            Welcome pObj = new Welcome("Ramakrishna Basgalla");

            Console.Read();
        }
    }
}

Output

In the above program we have created parameterized object for Welcome class, here the static constructor is called at the time of class load after then it's called corresponding parameterized constructor.

Destructors

.Net will clean up the un-used objects by using garbage collection process. It internally uses the destruction method to clean up the un-used objects. Some times the programmer needs to do manual cleanup.

Syntax

~<ClassName>
{}

Sample Program

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BRK.ConstructorExample
{
    class Welcome
    {
        // Default constructor
        public Welcome()
        {
            Console.WriteLine("Welcome message from Default Constructor...");
        }

        // Destructor
        ~Welcome()
        {
            Console.WriteLine("Destructor called");       
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            // Creating object for Welcome class
            // This will called default constructor
            Welcome obj = new Welcome();

            Console.Read();
        }
    }
}

Note: Destructor will call after execution of the program.

Let me know if you need any other technical articles in .Net.

HAPPY CODING.