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Classes

Classes are the fundamental building blocks of object-oriented programming (OOP) in C#. They act as blueprints or templates for creating objects, which are instances of classes. Classes encapsulate data (fields) and behavior (methods), providing a structured way to organize and manage related code.

Declaring Classes

Classes are declared using the class keyword followed by the class name and curly braces enclosing the class members:

class Car {

  // Fields (data)

  private string brand;

  private string model;

  private int year;

 

  // Methods (behavior)

  public void StartEngine() {

    Console.WriteLine("Car engine started.");

  }

 

  public void Accelerate() {

    Console.WriteLine("Car is accelerating.");

  }

 

  public void StopEngine() {

    Console.WriteLine("Car engine stopped.");

  }

}

 

Objects

Objects are instances of classes, representing specific entities in the real world. They encapsulate the state of the class (fields) and can execute the methods defined in the class.

Creating Objects

Objects are created using the new keyword followed by the class name and parentheses:

Car myCar = new Car(); // Create an object of the Car class

 

Accessing Class Members

Class members, both fields and methods, are accessed using the dot notation:

myCar.brand = "Toyota";

myCar.model = "Camry";

myCar.year = 2023;

 

myCar.StartEngine();

myCar.Accelerate();

myCar.StopEngine();

 

Example: Bank Account

Consider a bank account class:

class BankAccount {

  // Fields

  private string accountNumber;

  private double balance;

 

  // Methods

  public

 void

 Deposit(double amount) {

    balance += amount;

  }

 

  public

 void

 Withdraw(double amount) {

    if (amount <= balance) {

      balance -= amount;

    } else {

      Console.WriteLine("Insufficient funds.");

    }

  }

 

  public double GetBalance() {

    return balance;

  }

}

 

Creating an account object and performing operations:

BankAccount myAccount = new BankAccount();

 

myAccount.accountNumber = "12345678";

myAccount.balance = 500.00;

 

myAccount.Deposit(200.00);

Console.WriteLine("Balance after deposit: " + myAccount.GetBalance());

 

myAccount.Withdraw(300.00);

Console.WriteLine("Balance after withdrawal: " + myAccount.GetBalance());

 

Conclusion

Classes and objects are essential concepts in C# OOP, enabling the creation of structured, maintainable, and reusable code. Classes provide blueprints for objects, while objects encapsulate data and behavior, allowing programmers to model real-world entities and their interactions. Understanding classes and objects is crucial for developing effective C# applications.