C# Constructor

Description

Constructors run initialization code on a class or struct. They have the following features.

• A constructor initializes an object when it is created.
• A constructor has the same name as its class.
• A constructor is syntactically similar to a method.
• Constructors have no explicit return type.

Syntax

A constructor is defined like a method, except that the method name and return type are reduced to the name of the enclosing type:

The general form of constructor is shown here:

access class-name( ) {
// constructor code
}

Example

You can use a constructor to give initial values to the instance variables.

using System; /*  w  w  w  .j  a v a  2s. c  om*/
 
class MyClass { 
  public int x; 
 
  public MyClass() { 
    x = 10; 
  }   
}   
   
class ConsDemo {   
  public static void Main() {   
    MyClass t1 = new MyClass(); 
    MyClass t2 = new MyClass(); 
 
    Console.WriteLine(t1.x + " " + t2.x); 
  }   
}

The code above generates the following result.

Example 2

Constructors can have parameters. The following code uses the contructor to initialize the fields.

using System;//w ww .j a va2 s  . c  om

class Rectangle{
   public int Width;
   public int Height;
   public Rectangle(int w, int h){
      Width = w;
      Height = h;
   }
}

class Program
{

    static void Main(string[] args)
    {

        Rectangle r = new Rectangle(1, 2);

        Console.WriteLine(r.Width);
    }
}

The output: