Closures and Higher-Order Functions

Closures and Higher-Order Functions

In this lesson — part of Advanced Features — you'll learn closures and higher-order functions in C# and why it matters in real work.

Why it matters

Functions that take or return functions unlock concise, composable code.

Key ideas

• Functions as values
• map / filter / reduce
• Callbacks
• Composition

In practice

Here's how it looks in idiomatic C#:

using System.Linq;

var nums = new[] { 1, 2, 3, 4, 5, 6 };
var evensDoubled = nums
    .Where(n => n % 2 == 0)   // filter
    .Select(n => n * 2)       // map
    .ToList();
Console.WriteLine(string.Join(", ", evensDoubled)); // 4, 8, 12

C# note: In LINQ, 'Where' is filter and 'Select' is map; they are lazy and only execute when enumerated (here, by ToList).

Try it yourself

Exercise: In C#, use map and filter to get the squares of the even numbers.

Recap

You now understand closures and higher-order functions and can apply it in C#. Mark this lesson complete and continue to the next one.