Lambda Expression

A lambda expression is a short, inline function that can be used wherever a delegate or Func/Action is expected.

The => operator is read as “goes to”.

---

🔹 Syntax

(parameters) => expression

Or with a statement block:

(parameters) => { statements }

---

🔹 Examples

1. Basic Lambda (single expression)

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

• Func<int, int> → delegate type (input: int, output: int)

• x => x * x → function that returns x * x

---

2. Multiple parameters

Func<int, int, int> add = (a, b) => a + b; Console.WriteLine(add(3, 4)); // 7

---

3. Statement block

Action<string> greet = name => 
{
    string message = $"Hello, {name}!";
    Console.WriteLine(message);
};
greet("Alice"); // Hello, Alice!

• Action<T> → delegate type with no return value.

---

4. Using Lambda with LINQ

int[] numbers = {1, 2, 3, 4, 5};
var evenNumbers = numbers.Where(n => n % 2 == 0);  

foreach(var num in evenNumbers)
    Console.WriteLine(num); // 2, 4

• n => n % 2 == 0 is the lambda passed to Where().

---

🔹 Key Points

1. Lambda expressions are anonymous functions — no name needed.

2. They are short-hand for delegate implementations.

3. Can capture variables from outer scope (closures).

4. Often used in LINQ, events, callbacks, or functional-style programming.

---

✅ Summary:

• => = “goes to”

• (parameters) => expression = inline function

• Works with Func, Action, Predicate or any delegate type