Delegates in C#

Delgates are similar to a function pointer in C language.

A delegate is an object which stores the reference/address of a function.

A delegate can hold the reference of only those functions whose signature matches with that of a function.

Syntax:

<accessModifier> delegate <datatype> <nameofdelegate>(<arg1>,<arg2>)

There are 2 types of delegates:

1. Unicast delegate
2. Multicast delegate

1. Unicast delegate holds the reference of one function.

Example:

using System;
namespace unicast
{
    public delegate int AddDelegate(int x, int y);

    class program
    {
        static void Main()
        {
            AddDelegate dlg = new AddDelegate(Add);
            int r = dlg.Invoke(10, 20);
            Console.WriteLine("Sum is {0}", r);
            Console.ReadKey();
        }
        public static int Add(int x, int y)
        {
            return (x + y);
        }
    }
}

Output:

Sum is 30

2.

 

• Multicast delegate multicast delegate holds the reference of more than one function.
• Return type should be void.

Example:

using System;
namespace multicast
{
    public delegate void AddDelegate(int x, int y);

    class program
    {
        static void Main()
        {
            AddDelegate dlg = new AddDelegate(Add);
            dlg = dlg + new AddDelegate(Substract);
           dlg.Invoke(10, 20);

            Console.ReadKey();
        }
        public static void Add(int x, int y)
        {
            Console.WriteLine ("Sum is {0}",(x+ y));
        }
        public static void Substract(int x, int y)
        {
            Console.WriteLine("Difference is {0}", (x - y));
        }
    }
}

Output:

Sum is 30
Difference is -10