Delegates

Delegates in C# are type safe function pointers, which hold a reference to one or more methods
that have the same signature as that of a signature of a delegate.
Delegates are similar to functions pointers in C/C++.

Syntax:

delegate

We have 2 Types of Delegates.

- Single Cast Delegates: Delegates that reference a single method.

- Multi Cast Delegates: Delegates who hold reference to more than one method.

Example 1: Single Cast Delegate.

using System;
namespace SampleProgram {
//Delegate declaration
public delegate void MyDelegate(string Text);
class MyDelegateDemo {
public static void Greet(string info) {
Console.WriteLine("Hello" + info);
}
public static void Main() {
//declare the delegate and pass the method Greet as reference.
MyDelegate delGreet = new MyDelegate(Greet);
Console.WriteLine("Greet Here !!");
string info = Console.ReadLine();

//call the delegate, which will invoke the Greet() method
delGreet(info);
}
}
}

The output will be:

Greet Here!!
Good Morning!
Hello! Good Morning!

Multicast Delegate:

It is an extension of Single Cast Delegate. We can call more than one method using + operator in a multicast delegate.

- We have created 2 instances of SampleDelegate S1 and S2.

- S1 holds a reference to FirstMethod() and S2 holds a reference to the second method().

- S1+=S2; This statement will make S1 to point to both FirstMethod() as well as SecondMethod();

- Finally we invoke S1() which inturn will invoke both FirstMethod() and SecondMethod()

Example 2: Multi Cast Delegate.

Explanation:

- Two instances of delegates g1 and g2 created which reference to each greet method.

- g1+=g2 is equal to g1=g1+g2 which make g1 point to both methods.

- So g1() invokes both methods.

using System;
namespace SampleProgram {

//Delegate declaration
public delegate void MyDelegate();
class MyDelegateDemo {
public static void Greet1() {
Console.WriteLine( "Hello Good Morning !");
}
public static void Greet2() {
Console.WriteLine( "Hello Good Afternoon !");
}
public static void Main() {
MyDelegate g1 = new MyDelegate(Greet1);
MyDelegate g2 = new MyDelegate(Greet2);
g1 += g2;
g1();
}
}
}

The output will be:

Hello Good Morning!
Hello Good Afternoon!

Delegates

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