1.61. C# anonymous method

We have already mentioned that delegates are used to reference methods that have the same label as them. In other words, you can use a delegate object to call a method that can be referenced by a delegate.

Anonymous methods provide a technique for passing code blocks as delegate parameters. An anonymous method is a method that has no name but only a principal.

You do not need to specify a return type in an anonymous method, it is derived from the return statement inferred.

1.61.1. Write the syntax for anonymous methods #

Anonymous methods are done by using the delegate keyword to create a delegate instance to declare. For example:

delegate void NumberChanger(int n);
...
NumberChanger nc = delegate(int x)
{
    Console.WriteLine("Anonymous Method: {0}", x);
};

Code block Console.WriteLine("Anonymous Method: {0}", x); is the bodyof an anonymous method.

A delegate can be called either through an anonymous method or through a named method call, that is, by passing method parameters to the delegate object.

Note: the body of an anonymous method needs a ; .

For example:

nc(10);

1.61.2. Example #

The following example demonstrates the concept of anonymous methods:

Example #

using System;

delegate void NumberChanger(int n);
namespace DelegateAppl
{
    class TestDelegate
    {
        static int num = 10;
        public static void AddNum(int p)
        {
            num += p;
            Console.WriteLine("Named Method: {0}", num);
        }

        public static void MultNum(int q)
        {
            num *= q;
            Console.WriteLine("Named Method: {0}", num);
        }

        static void Main(string[] args)
        {
            // Creating a delegate instance using anonymous methods
            NumberChanger nc = delegate(int x)
            {
               Console.WriteLine("Anonymous Method: {0}", x);
            };

            // Using anonymous methods to call delegates
            nc(10);

            // Instantiating delegates using naming methods
            nc =  new NumberChanger(AddNum);

            // Calling delegates using named methods
            nc(5);

            // Instantiating a delegate using another naming method
            nc =  new NumberChanger(MultNum);

            // Calling delegates using named methods
            nc(2);
            Console.ReadKey();
        }
    }
}

When the above code is compiled and executed, it produces the following results:

Anonymous Method: 10
Named Method: 15
Named Method: 30