Why LINQ depends on extension methods in C Sharp (C#) - See It in Action

Why LINQ depends on extension methods

📖 Scenario: Imagine you have a list of numbers and you want to find all the even numbers easily. LINQ helps you do this in a simple way. Behind the scenes, LINQ uses something called extension methods to add new abilities to lists without changing their original code.

🎯 Goal: You will create a list of numbers, add an extension method to find even numbers, and then use it to get and print those even numbers.

📋 What You'll Learn

Create a list of integers called numbers with values 1, 2, 3, 4, 5, 6

Create a static class called MyExtensions with an extension method GetEvenNumbers for IEnumerable<int>

Use the extension method GetEvenNumbers on the numbers list to get even numbers

Print the even numbers separated by spaces

💡 Why This Matters

🌍 Real World

Extension methods let developers add useful features to existing classes without changing their code. This is how LINQ works to query collections easily.

💼 Career

Understanding extension methods is important for writing clean, reusable C# code and working with LINQ, which is widely used in software development.

1

Create the list of numbers

Create a list of integers called numbers with these exact values: 1, 2, 3, 4, 5, 6

C Sharp (C#)

# Create the list of numbers
// Your code here

Need a hint?

Use List<int> and initialize it with the values inside curly braces.

2

Create the extension method

Create a static class called MyExtensions and inside it create a public static extension method called GetEvenNumbers that takes this IEnumerable<int> source and returns only even numbers using a foreach loop and yield return

C Sharp (C#)

using System.Collections.Generic;

List numbers = new List { 1, 2, 3, 4, 5, 6 };

// Create static class MyExtensions with extension method GetEvenNumbers
// Your code here

Need a hint?

Extension methods must be inside a static class and have this before the first parameter.

3

Use the extension method to get even numbers

Create a variable called evenNumbers and set it to the result of calling numbers.GetEvenNumbers()

C Sharp (C#)

using System.Collections.Generic;

List numbers = new List { 1, 2, 3, 4, 5, 6 };

public static class MyExtensions
{
    public static IEnumerable GetEvenNumbers(this IEnumerable source)
    {
        foreach (int number in source)
        {
            if (number % 2 == 0)
            {
                yield return number;
            }
        }
    }
}

// Use the extension method to get even numbers
// Your code here

Need a hint?

Call the extension method directly on the numbers list.

4

Print the even numbers

Use a foreach loop to print each number in evenNumbers separated by spaces on one line

C Sharp (C#)

using System.Collections.Generic;

List numbers = new List { 1, 2, 3, 4, 5, 6 };

public static class MyExtensions
{
    public static IEnumerable GetEvenNumbers(this IEnumerable source)
    {
        foreach (int number in source)
        {
            if (number % 2 == 0)
            {
                yield return number;
            }
        }
    }
}

IEnumerable evenNumbers = numbers.GetEvenNumbers();

// Print the even numbers separated by spaces
// Your code here

Need a hint?

Use Console.Write inside the loop to print numbers on the same line separated by spaces.