C# Anonymous Functions

A type of function in C# which does not have a name is called anonymous function which can also be expressed as a function without a name. Anonymous functions are of two types in C# which are Lambda expressions in C# and Anonymous methods in C# where the anonymous function used to create delegates is called Lambda expression in C# using which local functions can be created and can be passed as an argument and the queries of LINQ can also be written with the help of Lambda expressions. The same functionality is provided by the Anonymous methods as well except that it allows to no use the list of parameters.

Types of Anonymous Functions in C#

There are two types of anonymous functions in C#. They are:

1. Lambda Expressions

• Delegates can be created by using a type of anonymous function called Lambda Expressions.
• Local functions can be created using Lambda expressions which can be passed as an argument.
• The queries of the LINQ can be written with the help of Lambda expressions.
• The syntax of lambda expression in C# is as follows:

(input-parameters) => expression

Example #1

C# program to demonstrate Lambda expression in a program to find the square of a number:

Code:

using System;
//a namespace called program is defined
namespace program
{
//a class called check is defined
class check
{
delegate int Findsquare(int number);
//main method is called
static void Main(string[] args)
{
//a lambda expression to find the square of a number is defined
Findsquare Obtainsquare = r => r * r;
int l = Obtainsquare(3);
Console.WriteLine("The Square of the given number is: "+l);
}
}
}

Output:

In the above program, a namespace called program is defined. Then a class called check is defined. Then the main method is called. Then a lambda expression is defined to find the square of a number. The square of the number found using the lambda expression is displayed.

Example #2

C# program to demonstrate Lambda expression in a program to determine if a number is present in the list or not:

Code:

using System;
using System.Collections.Generic;
//a namespace called program is defined
namespace program
{
//a class called check is defined
class check
{
//main method is called
static void Main(string[] args)
{
//a new list of type integer is created
List<int> mylist = new List<int>();
//integers are added to the list using add() method
mylist.Add(10);
mylist.Add(20);
mylist.Add(30);
//a lambda expression and find method is used to determine if a number is present in the list
int found = mylist.Find(r => r == 20);
if(found==0)
{
Console.WriteLine("The number is present in the list");
}
else
{
Console.WriteLine("The number is not present in the list");
}
//a lambda expression and find method is used to determine if a number is present in the list
found = mylist.Find(r => r == 40);
if(found==0)
{
Console.WriteLine("The number is present in the list");
}
else
{
Console.WriteLine("The number is not present in the list");
}
}
}
}

Output:

In the above program, a namespace called program is defined. Then a class called check is defined. Then the main method is called. Then a new list of type integer is created. Then integers are added to the list using the Add() method. Then a lambda expression along with Find() method is used to determine is a number is present in the list or not.

2. Anonymous Methods

• A method which does not have a name is called an anonymous method in C#.
• The anonymous method was introduced in C# version 2.0.
• We make use of anonymous methods when an inline method is to be created and parameters also must be passed to the method similar to the way we pass parameters to any other methods.
• The keyword delegate is used to define an anonymous method and this method can be assigned to a variable of type delegate.
• The syntax of Anonymous method in C# is as follows:

Delegate(parameter_list)
{
//Block of code
};

Example #1

C# program to demonstrate an anonymous method in a program:

Code: 

using System;
//a class called program is defined
class program
{
//a delegate is created by using delegate keyword
public delegate void subject(string favsubject);
// Main method is called
static public void Main()
{
// a parameter is passed to the anonymous method using delegate keyword
subject sub = delegate(string favsubject)
{
Console.WriteLine("{0} is my favourite subject", favsubject);
};
sub("C#");
}
}

Output:

In the above program, a class program is defined. Then a delegate is created by using the delegate keyword. Then the main method is called. Then a parameter is passed to the anonymous method using the delegate keyword.

Example #2

C# program to demonstrate an anonymous method in a program that can access a variable which is defined in the outer method:

Code: 

using System;
//a class called program is defined
class program
{
//anonymous method is declared using delegate keyword
public delegate void subject(string favsubject);
// Main method is called
static public void Main()
{
//a string variable is defined in the outside method from anonymous method
string favsubject1 = "Coding_in_C#";
// a parameter is passed to the anonymous method using delegate keyword
subject sub = delegate(string favsubject)
{
Console.WriteLine("{0} is my favourite subject", favsubject);
Console.WriteLine("I also like {0}", favsubject1);
};
sub("C#");
}
}

Output:

In the above program, a class called program is defined. Then a delegate is created using the delegate keyword. Then the main method is called. Then a string variable is defined which is the outside method from the anonymous method. Then a parameter is passed to the anonymous method using the delegate keyword. The anonymous method access the variable outside the anonymous method also.

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