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Lesson 2120 min read

Classes & Objects

Learn the foundation of Object-Oriented Programming in C#: classes, objects, fields, and methods.

What is a Class?

A class is a blueprint that defines what data (fields) and behavior (methods) its objects will have. It doesn't take up memory on its own — it's a template.

What is an Object?

An object is a concrete instance of a class, created using the `new` keyword. Each object has its own independent copy of the class's fields.

class Car
{
    public string Model;
    public int Year;


    public void Honk()
    {
        Console.WriteLine($"{Model} says beep beep!");
    }
}


var myCar = new Car { Model = "Civic", Year = 2022 };
myCar.Honk();
Output

Click Run to see what this code prints.

Fields and Methods

Fields store an object's data; methods define what it can do. Together they model a real-world concept as code.

Creating Multiple Objects

var car1 = new Car { Model = "Civic", Year = 2022 };
var car2 = new Car { Model = "Corolla", Year = 2023 };


Console.WriteLine(car1.Model); // Civic
Console.WriteLine(car2.Model); // Corolla — completely independent
Each Object is Independent

Since Car is a reference type, car1 and car2 are two separate objects on the heap, each with its own fields — changing one never affects the other.

FAQs

No — value types like `int` and `bool` are structs, not classes, though C#'s type system treats them consistently in most respects.

Summary

  • A class is a blueprint; an object is an instance of that blueprint.
  • Fields hold data, methods define behavior.
  • Each object created with `new` has its own independent data.
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Constructors