Anonymous Methods

An anonymous method is a block of code that is passed to a delegate. It is created only to be used as a target for a delegate. The main advantage to using an anonymous method is simplicity.

Example:

// Demonstrate an anonymous method
using system;

// Declare a delegate type

delegate void ShowSum();

class AnonymousMethod

{

  static void Main()

  {

    // The code for generating the sum is passed as an anonymous method

    ShowSum oShowSum = delegate

    {

      // This is the block of code passed to the delegate

      int iSum = 0;

      for(int i = 0;  i <= 5; i++)

      {

        iSum += i;

      }

      Console.Writeline(iSum);

    }; // Notice the semicolon

  }

}

Output: 15

Pass Arguments and Return a Value from an Anonymous Method

It is possible to pass one or more arguments to an anonymous method. To do so, follow the delegate keyword with a parenthesized parameter list. Then, pass the argument(s) to the delegate instance when it is called.

An anonymous method can also return a value. However, the type of the return value must be compatible with the return type specified by the delegate.

Example:

// Demonstrate an anonymous method that returns a value.

using System;

// This delegate returns a value. Notice that ShowSum now has a parameter.

delegate int ShowSum(int iEnd);
class AnonymousMethod
{
  static void Main()
  {
    int result;   
    // Here, the ending value for the count is passed to the anonymous method.
    // A summation of the count is returned.

    ShowSum oShowSum = delegate (int iEnd)
    {
       int iSum = 0;
       for(int i=0; i <= iEnd; i++)
       {
         Console.WriteLine(i);
         iSum += i;
       }
       return iSum;  // Return a value from an anonymous method
    };

    result = oShowSum(3);
    Console.WriteLine("Summation of 3 is " + result);
    Console.WriteLine();

    result = oShowSum(5);
    Console.WriteLine("Summation of 5 is " + result);
  }
}

Related Post: Delegates, Multicast Deletages (Multicasting)