Class and Objects in C# with Examples

Hi Guys, Welcome in my online tutorials.

In this online tutorial, I am going to explain you the basic understanding of Class and Objects in C# with multiple examples. 

Before proceeding to this article, please read our previous article where we discussed the basics concepts of Object-Oriented Programming.

For every developer, Understanding of class and objects in C# is very important. Because everything in C# is in the form of class and objects.

In this tutorial, we are going to cover the following basic questions in detail to understand the Class and Objects.

1. Class and Objects in general term?
2. What is a Class in C#?
3. What are the different Types of classes in C#?
4. How to create a class in C#?
5. How to create objects in C#?
6. Difference between Class and Objects in C#.

 

Class and Objects in general term.

In simple term, Class is a template or blueprint with state and behavior. State is called properties of a class and behavior is called actions in a class.

Ex: Employee has the properties like Id, Name, Address etc. and actions like AccountDetails, SalaryDetails etc.

In simple term, Object is an instance of a class.

Ex: If we consider the Employee in a company. Director, CTO, CEO, Manager, Team Leader, Sr. Developer, Developer, etc. all are object of that class Employee.

What is a Class in C#?

We know that Class is a template or blueprint with state and behavior. State is called properties of a class and behavior is called actions in a class.

Remember: Action is called method or function in C#.

We know that C# is an object-oriented programming language, so a program is designed with objects and classes. A class is a code block that is used for grouping properties/variables and methods/functions for developing functionality logic.

 

 

What are the different Types of classes in C#?

In general we use below 5 types of classes in C#:

1.   Static class

2.   Sealed class

3.   Partial class

4.   Concrete class

5.   Abstract class

Using access modifier we are restricting the accessibility of the classes to the other classes.

Access modifiers are mainly 5 types:

1. Public
2. Private
3. Protected
4. Internal
5. Protected internal

Key features of a class:

1. Class is a reference type. It means it hold the object reference that is created dynamically in a heap.
2. The base type of a class is System.Object.
3. Default access modifier of a class is Internal.
4.  Default access modifier of properties/ variables and methods is Private.
5.  Private classes are not allowed directly inside the namespaces.

 

How to create a Class in C#?

The general form to create a class is as below:

<access modifier> class ClassName

{

//Properties/variables of this class

<access modifier> <return type> property1

<access modifier> <return type> property2

….

<access modifier> <return type> propertyn

//methods of this class

<access modifier> <return type> method1(parameters)

{

//method1 body

}

<access modifier> <return type> method2(parameters)

{

//method2 body

}

….

<access modifier> <return type> methodn(parameters)

{

//methodn body

}

}

Remember: access modifier describe the accessibility, Data type describe the type of variable, and return type describe the data type of the data, the method returns if any.

 

Ex:

using System;

namespace EHDApplication {

Public class Employee {

      private string  id { get; set; }  // Id of the Employee

      public string name { get; set; } // Name of the Employee

      private int age { get; set; };   // Age of the Employee

      public string Department { get; set; }// Department of the Employee

      public dynamic UserDetails(string  Id) {

         // Employee User Detail logic

      }

      public dynamic MonthlySalary(string  Id) {

         // Employee Monthly Salary logic

      }

    }

How to create an Object in C#?

We already discussed that an Object is a real-world entity. It is a collection of leaving and non-leaving things. For example, Person, Animal, mobile, laptop, pen, etc. In general object is an entity that has state and behavior. Here, state means data and behaviors means functionality.

Object is created at runtime, that’s why it is called a runtime entity.

It is an instance of a class. We can access all the members of a class through the object. Use the dot (.) notation to access the members of a class.

 

Ex: We can create an object using the new keyword.

Employee myEmployee = new Employee(); //creating an object of Employee 

In this example, Employee is the type and myEmployee is the reference variable that refers to the instance of Employee class. The new keyword allocates memory at runtime in the Heap.

 

Example: Employee class that has three properties: id, name, and department. It creates an instance of the class Employee, initializes the object and prints the object value.

using System;

namespace EHDApplication {

public class Employee

{

// Declare properties/variabls

Id { get; set; }  // Id of the Employee

int id { get; set; }  // Id of the Employee, by default id is Private member

string name { get; set; }  // by default name is Private member

string department { get; set; }  // by default department is Private member

public static void Main(string[] args)

{

//creating an object of Employee class

Employee myEmployee = new Employee();

//Object initialization

myEmployee.id = 1001;

myEmployee.name = "Donald Trump";

myEmployee.department = "IT";

//Printing the values

Console.WriteLine("Employee ID : " + myEmployee.id);

Console.WriteLine("Employee Name : " + myEmployee.name);

Console.WriteLine("Employee Department : " + myEmployee.department);

}

}

}

OUTPUT:

Employee ID: 1001

Employee Name: Donald Trump

Employee Department: IT

Example: If Main () method in another class then how can access class members.

Remember: In this case class must be public and we need to specify the class member as public.

using System;

namespace EHDApplication {

public class Employee

{

public int id{ get; set; } 

public String name{ get; set; }

public string department{ get; set; } 

}

public class EmployeeDemo

{

public static void Main(string[] args)

{

// creating an object of Employee class

Employee myEmployee = new Employee();

//Object initialization

myEmployee.id = 1001;

myEmployee.name = "Donald Trump";

myEmployee.department = "IT";

//Printing the values

Console.WriteLine("Employee ID : " + myEmployee.id);

Console.WriteLine("Employee Name : " + myEmployee.name);

Console.WriteLine("Employee Department : " + myEmployee.department);

}

}

}

OUTPUT:

Employee ID: 1001

Employee Name: Donald Trump

Employee Department: IT

Example: Initialize and Display data through a method

In this example we are initializing and displaying an object through the method.

using System;

namespace EHDApplication {

public class Employee

{

public int id{ get; set; } 

public String name{ get; set; }

public string department{ get; set; } 

public void InsertEmployData(int ID, string Name, string Department)

{

id = ID;

name = Name;

department = Department;

}

public void DisplayEmployeeData()

{

Console.WriteLine("Employee ID : " + id);

Console.WriteLine("Employee Name : " + name);

Console.WriteLine("Employee Department : " + department);

}

}

public class EmployeeDemo

{

public static void Main(string[] args)

{

//creating two objects of Employee class

Employee myEmployee1 = new Employee();

Employee = new Employee();

//Initializing the Employee Object myEmployee1 using method

myEmployee1. InsertEmployData (1001, "Donald Trump ", "IT");

//Initializing the Employee Object myEmployee2 using method

myEmployee2. InsertEmployData (1002, "John Smith", "HR");

myEmployee1. DisplayEmployeeData ();

myEmployee2. DisplayEmployeeData ();

}

}

}

OUTPUT:

Employee ID: 1001

Employee Name: Donald Trump

Employee Department: IT

Employee ID: 1002

Employee Name: John Smith

Employee Department: HR

 

What are the difference between Class and Objects in C#

We learned that Class is a template for Objects.

Each and every Object must belong to a specific Class.

    

Remember: All Objects share the same copy of the methods, but maintain a separate copy of the member data (Properties or fields).

Ex: In previous example Employee class have separate copy of the member data (Properties or fields).

Employee ID: 1001

Employee Name: Donald Trump

Employee Department: IT

Employee ID: 1002

Employee Name: John Smith

Employee Department: HR

But share the same copy of the methods:

InsertEmployData() & DisplayEmployeeData ()

The main difference between class and object is as below:

Class	Object
Class is a template/blueprint for Objects	Instance of a class
It is used to bind data and methods in a single unit.	It is used as a variable of a class
It does not take any memory spaces after executing the code.	It take memory spaces in heap after executing the code.

In this article, I try to explain Class and Objects in C# with some examples. I hope you understood class and objects in C#. In the next article, I am going to discuss Constructors in C# and its types in details with examples.