Delegates in C#

A delegate in C# is a reference to the method. A delegate is a reference type variable that holds the reference to a method. The reference can be changed at runtime.

Delegates are especially used for implementing events and the call-back methods. All delegates are implicitly derived from the System.Delegate class.

Let us see how to declare delegates in C#.

delegate <return type> <delegate-name> <parameter list>

Let us see an example to learn how to work with Delegates in C#.

Example

 Live Demo

using System; using System.IO; namespace DelegateAppl {    class PrintString {       static FileStream fs;       static StreamWriter sw;       // delegate declaration       public delegate void printString(string s);       // this method prints to the console       public static void WriteToScreen(string str) {          Console.WriteLine("The String is: {0}", str);       }       // this method prints to a file       public static void WriteToFile(string s) {          fs = new FileStream("c:\message.txt",          FileMode.Append, FileAccess.Write);          sw = new StreamWriter(fs);          sw.WriteLine(s);          sw.Flush();          sw.Close();          fs.Close();       }       // this method takes the delegate as parameter and uses it to       // call the methods as required       public static void sendString(printString ps) {          ps("Hello World");       }       static void Main(string[] args) {          printString ps1 = new printString(WriteToScreen);          printString ps2 = new printString(WriteToFile);          sendString(ps1);          sendString(ps2);          Console.ReadKey();       }    } }

Output

The String is: Hello World