Coding Test: Extension method

Create an extension method to filter out odd and even numbers from a collection like a list or array. Below is an example of how you can write such extension methods.

1. Extension Method to Filter Odd Numbers

This method filters odd numbers from a collection of integers.

using System;

using System.Collections.Generic;

public static class NumberExtensions

{

    // Extension method to get odd numbers from an IEnumerable<int>

    public static IEnumerable<int> GetOddNumbers(this IEnumerable<int> numbers)

    {

        foreach (var number in numbers)

        {

            if (number % 2 != 0)

            {

                yield return number;

            }

        }

    }

    // Extension method to get even numbers from an IEnumerable<int>

    public static IEnumerable<int> GetEvenNumbers(this IEnumerable<int> numbers)

    {

        foreach (var number in numbers)

        {

            if (number % 2 == 0)

            {

                yield return number;

            }

        }

    }

}

class Program

{

    static void Main(string[] args)

    {

        List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

        // Filter odd numbers using extension method

        var oddNumbers = numbers.GetOddNumbers();

        Console.WriteLine("Odd Numbers:");

        foreach (var number in oddNumbers)

        {

            Console.WriteLine(number);

        }

        // Filter even numbers using extension method

        var evenNumbers = numbers.GetEvenNumbers();

        Console.WriteLine("Even Numbers:");

        foreach (var number in evenNumbers)

        {

            Console.WriteLine(number);

        }

    }

}

Output: 

Odd Numbers: 1 3 5 7 9 Even Numbers: 2 4 6 8 10

Summary:

• The GetOddNumbers and GetEvenNumbers methods are simple extension methods that work on any collection implementing IEnumerable<int>.
• yield return is used in the methods to lazily return the filtered numbers without creating a new list upfront, making it memory efficient.