Creating and Using Classes

What is a Class?

A class is a blueprint for objects. It defines properties (data) and methods (behavior). You can create multiple objects (instances) from a single class definition.

public class Person
{
    public string Name;
    public int Age;

    public void Introduce()
    {
        Console.WriteLine($"Hi, I'm {Name} and I'm {Age} years old.");
    }
}

Creating and Using an Object

Here’s how you can create an object of the class and use its members:

Person person = new Person();
person.Name = "Alice";
person.Age = 30;
person.Introduce();

Using Constructors

A constructor is a special method that runs when an object is created. Use it to initialize values.

public class Book
{
    public string Title;
    public string Author;

    public Book(string title, string author)
    {
        Title = title;
        Author = author;
    }
}

Book b = new Book("C# Basics", "Jane Doe");
Console.WriteLine(b.Title);

Access Modifiers

Access modifiers control how a class or its members can be accessed:

• public – accessible from anywhere
• private – accessible only within the class
• protected – accessible from the class and its subclasses
• internal – accessible within the same project/assembly

Best Practices for Defining Classes

• Use PascalCase for class and method names
• Group related logic into separate classes (e.g., Customer, Order)
• Encapsulate data using properties instead of public fields
• Keep classes focused on a single responsibility

Classes allow you to write modular and reusable code. In the next lesson, we’ll cover how to perform input and output operations in console applications, including reading from the user and writing to files.