C# Lambda Expression

Lambda Expressions have been part of .NET since version 3.5 (C# 3.0); so, I decided to add a quick tutorial to the blog for programmers new to C# or C# 3.0+.

Quick Definition

“A lambda expression is an anonymous function that can contain expressions and statements, and can be used to create delegates or expression tree types.”

From MSDN Site

In sum, a lambda expression is a way we can implement an anonymous method in less code. Besides the syntactic benefits added by Lambda expression; they also bring elements of functional programming into C# (a traditional object oriented language).

To the point

A lambda expressions must being with a parameter or set of parameters followed by the lambda symbol (=>) then the expression to be executed.

Syntax Form:

Parameter(s) => Expressions

Example 1:

X => X * 2

The example shows a function where X is the parameter following by the return expression of (X * 2).

Example 2:

Let’s declare a delegate.

public delegate int DoubleIt(int v);

Back in C# 2.0 we would have to use an anonymous method (see example below):

DoubleIt d = new DoubleIt(delegate(int x) {

     return x * 2;

 });

Console.WriteLine(d(3));

We can still use an anonymous methods; however, we can also use lambda expressions to accomplish the same thing (see example below):

DoubleIt d =  x => x * 2;

Console.WriteLine(d(3));

Example 3:

Lambda expression with multiple arguments

Let’s declare a delegate.              

public delegate int Multiply(int a, int b);

…

Multiply multi = (a, b) => a * b;

Console.WriteLine(multi(2, 3));

Lambda Statements

Lambda statements follow the same principle as expression; but, it encloses a full statement within brackets.

Syntax Form:

Parameter(s) => { Statement }

Example 4:

X => { Return  X * 2; }

Example 5:

Lambda statement that returns void

Let’s declare a delegate.

delegate void Greeter(string name);

...

Greeter g = new Greeter((string name) => {

                Console.WriteLine("Hello " + name);

            });

g("Walter");

Or

Greeter g = name => { string r = "Hello " + name; Console.WriteLine(r); };

g("Walter");

Output:

Hello Walter

Summary

The purpose of this post was to show you a basic implementation of lambda expressions in C# via examples without touching the functional programming subject.