C# Classes Examples

A class is basic pillar of OOP that is called when instance of a class is created. A class can have fields, properties, method, constructor and destructor etc. When we create an instance of class. This instance of class is used to access of fields, methods, properties, constructor (constructor can zero argument or multiple argument) and destructor. A class is reference type and stores in heap.

Here, below is a Fruit class diagram that we explained with code and description.

Some Important Features Of Classes in C#

• Data Member Declaration:

  You declare an attribute and variable of class in such way.

  Declaration and Initialization: Example

  Here, in below example of integer type field

  • private - Here, below private is access modifier.

  • int - int is data type

  • FruitPrice - FruitPrice is a vairable name

  Here, in below example of string type field

  • private - Here, below private is access modifier.

  • string - string is data type

  • FruitName - FruitName is a vairable name.

  Here, in below example of boolean type field

  • private - Here, below private is access modifier.

  • bool - bool is data type.

  • FruitIsInMarket - FruitIsInMarket is a vairable name.

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  // Fields (attributes or variables)

  private int FruitPrice;

  private string FruitName;

  private bool FruitIsInMarket;

• Data Member Initialization:

  You can initialize an attribute and variable of class in such way.

  Data Member Initialization: Example

  Here, in below example

  • FruitPrice = 100; - Here, FruitPrice has int value 100.

  • FruitName = Mango; - FruitName has string value Mango.

  • FruitIsInMarket = Yes; - FruitIsInMarket has bool value Yes.

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  // Initializing data member of class

  FruitPrice = 100;

  FruitName = Mango;

  FruitIsInMarket = Yes;

• Constructor In Class:

  Constructor is special method that called when object/instance of class is created

  Constructor In Class: Example

  Here, in below example

  • public Fruit(int price, string name, bool Isavailable ) - Here, Fruit is an 3-argument constructor that have parameter price,name, Isavailable

  • FruitPrice = price; - price parameter is assigned to field FruitPrice.

  • FruitName = name; - name parameter is assigned to field FruitName.

  • FruitIsInMarket = Isavailable; - Isavailable parameter is assigned to field FruitIsInMarket.

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  // Constructor

  public Fruit(int price, string name, bool Isavailable )

  {

  FruitPrice = price;

  FruitName = name;

  FruitIsInMarket = Isavailable;

  }

• Destructor In Class:

  Destructor is also a special method that called when object/instance of class is destroyed.

  Destructor In Class: Example

  Here, in below example

  • ~Fruit() - Here, ~Fruit is an destructor that will call when Fruit class instance will be destroyed.

  • Console.WriteLine("Fruit Instance is Destroyed"); - Print a value.

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  ~Fruit()

  {

  Console.WriteLine("Fruit Instance is Destroyed");

  }

• Method In Class:

  You can defined the method or function of class in sunch way

  Method In Class: Example

  Here, in below example

  • publicvoid GetFruit() - Here, GetFruit() is method or function name that does not have return type and it is accessible outside the class.

  • Console.WriteLine("This is a collection of fruits); - Print a value if function successfully call.

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  // Methods (functions or behaviors)

  public void GetFruit()

  {

  Console.WriteLine("This is a collection of fruits);

  }

• Instance of Class:

  You can create instance of class in C# such a way.

  Instance of Class: Example

  Here, in below example

  • Fruit objFruit = new Fruit(20,"Mango",true); - Here, objFruit is an instance of Fruit class that has 3 parameter with named 20, Mango, true.

  • objFruit.GetFruit(); - We are calling GetFruit() method of Fruit Class with the instance objFruit.

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  // Creating an instance of Fruit Class

  Fruit objFruit = new Fruit(20,"Mango",true);

  // Calling a method

  objFruit.GetFruit();

• Classes: Example

  In below example we have Fruit class and have some feilds amd constructor and methods.

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  using System;

  public class CSharpTutorial

  {

  public static void Main(string[] args)

  {

  Fruit objFruit = new Fruit(20,"Mango",true);

  // Calling a method

  objFruit.GetFruit();

  // Accessing a field fruit price

  int fieldPrice = objFruit.GetFruitPrice();

  // Accessing a field fruit name

  string fieldName = objFruit.GetFruitName();

  // Accessing a field fruit is in market

  bool fieldIsInMarket = objFruit.GetFruitIsInMarket();

  Console.WriteLine("Fruit name: " + fieldName + " Fruit price:" + fieldPrice + " Is available in market :" + fieldIsInMarket);

  }

  }

  public class Fruit

  {

  // Fields (attributes or variables)

  private int FruitPrice;

  private string FruitName;

  private bool FruitIsInMarket;

  // Constructor

  public Fruit(int price, string name, bool Isavailable)

  {

  FruitPrice = price;

  FruitName = name;

  FruitIsInMarket = Isavailable;

  }

  // Methods (functions or behaviors)

  public void GetFruit()

  {

  Console.WriteLine("This is a collection of fruits");

  }

  // Methods (functions or behaviors)

  public int GetFruitPrice()

  {

  return FruitPrice;

  }

  public string GetFruitName()

  {

  return FruitName;

  }

  public bool GetFruitIsInMarket()

  {

  return FruitIsInMarket;

  }

  }

  
  
  

  Output

  This is a collection of fruits

  Fruit name: Mango Fruit price:20 Is available in market :True

• Main entry point description

  Here's a basic breakdown of how Main entry point of Fruit class work in C#:
  using System;	using System; is namespace of C# that required to run the above program.
  CSharpProgram	We have defined a class CSharpProgram that will contain function or methods.
  static void Main(string[] arge)	It is a main entry point of the program.
  Fruit objFruit = new Fruit(20,"Mango",true);	Here, objFruit is an instance of Fruit class that has 3 parameter with named 20, Mango, true.
  int fieldPrice = objFruit.GetFruitPrice();	Here, we are calling GetFruitPrice() method and storing it in fieldPrice.
  string fieldName = objFruit.GetFruitName();	Here, we are calling GetFruitName() method and storing it in fieldName.
  bool fieldIsInMarket = objFruit.GetFruitIsInMarket();	Here, we are calling GetFruitIsInMarket() method and storing it in fieldPrice.
  Console.WriteLine("Fruit name: " + fieldName + " Fruit price:" + fieldPrice + " Is available in market :" + fieldIsInMarket);	Here, we are printing fieldPrice, fieldName and fieldIsInMarket.

• Class Example Deccription in C#:

  Here's a basic breakdown of how Class work in C#:
  public class Fruit	Here Fruit is an public class.
  private int FruitPrice; private string FruitName; private bool FruitIsInMarket;	FruitPrice,FruitName and FruitIsInMarket are fields of class Fruit that have int, string and bool data type respectively and these fields are private because they are only accessible inside the class.
  public Fruit(int price, string name, bool Isavailable) { FruitPrice = price; FruitName = name; FruitIsInMarket = Isavailable; }	This code is an example of 3-argument constructor of Fruit class and here we are assigning the Fruit class constructor passing parameter to the fields of the Fruit class.
  public int GetFruitPrice() { return FruitPrice; }	Here, Fruit Class has GetFruitPrice() method that will return FruitPrice of Fruit class
  public string GetFruitName() { return FruitName; }	Here, Fruit Class has GetFruitName() method that will return FruitName of Fruit class
  public bool GetFruitIsInMarket() { return FruitIsInMarket; }	Here, Fruit Class has GetFruitIsInMarket() method that will return FruitIsInMarket of Fruit class

Summary

Classes are main pillar of Of C# and Object-Oriented programming (OOP). The class enable you to keep code neat and clean and enhance code reusability and help us to manage real-world entities in best way in your application with fields, methods, constructor, destructor.