Important C# Topics

Extension Methods

Add discoverable operations to existing types.

Introduction

Extension methods are static methods called with instance syntax.

The this modifier on the first parameter declares an extension target. The original string type is not modified.

Runnable C# example

Program.cs

using System;

static class StringExtensions
{
    public static string Truncate(this string value, int length)
        => value.Length <= length ? value : value[..length] + "…";
}

class Program
{
    static void Main() => Console.WriteLine("CodeUtility".Truncate(4));
}

Result of running the code

Code…

Practice with the debugger

Set a breakpoint on an important assignment or condition, click Debug, and inspect the local values before stepping to the next line.

Practice with a challenge

Use what this lesson covers to solve a real problem. Each challenge runs in your browser with instant tests and an AI review.

Title Case Capitalize the first letter of every word. Easy
Acronym Generator Create an acronym from the first letter of every word, in uppercase. Easy

All challenges