C# Classes and Objects

The Building Blocks You Use Every Day

Everything you write in C# lives inside a class. Here’s how they actually work.

AI Generated

If you’ve written even a few lines of C#, you’ve used a class. But there’s a difference between using classes and understanding them. Once the mental model clicks, everything else — inheritance, interfaces, design patterns — starts to make sense.

Let’s build that model from scratch.

What Is a Class?

A class is a blueprint. It describes what something is and what it can do.

Think of a class like an architect’s floor plan. The plan itself isn’t a house — it’s the description of a house. You use it to build as many actual houses as you want.

public class Car
{
    public string Brand;
    public string Color;
    public int Year;

    public void StartEngine()
    {
        Console.WriteLine($"{Brand} engine started!");
    }
}

That’s a class. It defines that a Car has a brand, a color, a year, and can start its engine. No actual car exists yet — just the blueprint.

What Is an Object?