Lambda expressions in C# provide a concise way to create anonymous functions. They are a powerful feature introduced in C# 3.0, enabling developers to write more expressive and functional code.

What are Lambda Expressions?

Lambda expressions are inline, anonymous functions that can be used to create delegates or expression tree types. They allow you to write local functions that can be passed as arguments or returned as values from other functions.

Basic Syntax

The basic syntax of a lambda expression consists of input parameters (if any), the lambda operator =>, and an expression or statement block.

(parameters) => expression

For single-parameter lambda expressions, parentheses are optional:

parameter => expression

Examples of Lambda Expressions

1. Simple Lambda Expression

Func<int, int> square = x => x * x;
Console.WriteLine(square(5)); // Output: 25

In this example, we define a lambda expression that squares a number. The Func<int, int> delegate takes an integer input and returns an integer output.

2. Lambda with Multiple Parameters

Func<int, int, int> add = (x, y) => x + y;
Console.WriteLine(add(3, 7)); // Output: 10

Here, we create a lambda expression that adds two numbers. The delegate takes two integer inputs and returns their sum.

Common Use Cases

Lambda expressions are frequently used in various scenarios:

With LINQ queries for filtering, sorting, and transforming data
As event handlers or callbacks
In functional programming patterns
For creating short, inline functions

Lambda Expressions in LINQ

One of the most common applications of lambda expressions is in LINQ queries. They provide a concise way to define predicates and projections.

List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
var evenNumbers = numbers.Where(n => n % 2 == 0);
foreach (var num in evenNumbers)
{
    Console.WriteLine(num);
}
// Output: 2, 4, 6, 8, 10

In this example, the lambda expression n => n % 2 == 0 is used to filter even numbers from the list.

Best Practices and Considerations

Keep lambda expressions short and simple for better readability
Use lambda expressions to reduce code duplication
Consider using lambda expressions instead of anonymous methods for more concise code
Be aware that extensive use of lambda expressions can make debugging more challenging

Conclusion

Lambda expressions are a powerful feature in C# that enable more expressive and functional programming styles. They are particularly useful in scenarios involving delegates, LINQ queries, and event handling. By mastering lambda expressions, you can write more concise and efficient code in your C# applications.