C# 0 The Complete Reference

obj

, which is an 

object

 reference. The integer value in 

obj

 is retrieved by casting 

obj

to

int

.

Here is another, more interesting example of boxing. In this case, an 

int

 is passed as an 

argument to the 

Sqr( )

 method, which uses an 

object

 parameter.

// Boxing also occurs when passing values.

using System;

class BoxingDemo {

  static void Main() {

    int x;

    x = 10;

    Console.WriteLine("Here is x: " + x);

    // x is automatically boxed when passed to Sqr().

    x = BoxingDemo.Sqr(x);

    Console.WriteLine("Here is x squared: " + x);

  }

  static int Sqr(object o) {

    return (int)o * (int)o;

  }

}

The output from the program is shown here:

Here is x: 10

Here is x squared: 100

Here, the value of 

x

 is automatically boxed when it is passed to 

Sqr( )

.

Boxing and unboxing allow C#’s type system to be fully unified. All types derive from 

object

. A reference to any type can be assigned to a variable of type 

object

. Boxing and 

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