functional-workshop

functional programming principles applied in C#

---

Project maintained by B1tF8er Hosted on GitHub Pages — Theme by mattgraham

Extension Methods

Extension methods enable you to “add” methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type.

• They are just static methods in a static class
• Enable the Open/Close principle
• Enable method chaining

using System;
using static System.Console;

internal class TestExtensionMethods
{
    internal static void Run()
    {
        var person = new Person("George", 30);
        WriteLine(person);
        WriteLine($"Days lived from person object {person.DaysLived()}");
        WriteLine($"Days lived from Age property {person.Age.DaysLived()}");
    }
}

internal class Person
{
    internal string Name { get; }
    internal int Age { get; }

    internal Person(string name, int age)
    {
        Name = name;
        Age = age;
    }

    public override string ToString() => $"My name is {Name} and I am {Age} years old";
}

internal static class PersonExtensions
{
    internal static int DaysLived(this Person person) =>
        person.Age * 365;

    internal static int DaysLived(this int age) => age * 365;
}