C# Class and Object

In the C# programming language, the class and object are the fundamental components of OOP (Object Oriented Programming). They provide the code in a more organized, reusable, and maintainable way. In C#, classes act like a blueprint that defines how objects are structured and behave in the program. On the other hand, objects are instances of classes that are used to hold data and methods to create and manipulate several entities.

C# Classes

In OOP, a class is a fundamental building block that collects the data members and data methods into a single unit. It is a user-defined reference type that acts as a blueprint to create objects. A class keyword is used to create a class in C#.

A class helps in code reusability and portability, which means the same class can be used across different programs without rewriting the code. It also supports encapsulation, which means it hides the internal implementation details of a class and shows only the necessary features to the outside world. It can also contain fields, properties, methods, constructors, and events.

Syntax

It has the following syntax.

In this syntax,

• Data Members: The data members are the variables that are defined inside the class of the program.
• Data Method: The data method is the functions that are also defined in the class of the program that operate on the data members.
• Access Specifiers: These are utilized to define the visibility and access of a class and its members. These specifiers access the class, field, property, and method.

Let us take an example to define a class in C#.

Output:

The student's name is John
The student's age is 20

Explanation:

In this example, we define the class named Student. Inside this class, we create the methods named DisplayInfo and a member named "name" and "age" that display the details of the student.

After that, we create an object of the class Student and assign the values "John" and 20 to the object's name and age. Finally, we use the Console.WriteLine() function to print the output.

C# Class Access Specifiers

In the C# programming language, the access specifiers are used to control access to class members. The access specifier is also known as an access modifier in C#.  These are the keywords that are used to limit the accessibility of data members and methods, including protected, private, public, and internal.

There are mainly four types of access specifiers in C#.

• Public Specifier: In C#, the public is a more flexible specifier. The public members of a class will be accessible from anywhere in the program.
• Private Specifier: The private members are the more restrictive specifiers in C#. The data members of a class will be accessible inside the code block where they were declared.
• Protected Specifier: The protected members of the class will be accessible within the same class and also inside its derived classes.
• Internal Specifier: The internal specifiers are of assembly-level specifiers. The internal member of the class that can be accessed within the same assembly.

To Read More: Access Modifiers in C#

C# Object

An object is a run-time entity (such as a chair, a car, a pen, etc.) that is used to represent the features of a class. It is also known as an instance of a class, which defines its structure, behaviour, and identity. It is created in the memory when the program is executed. Objects are used to hold data in fields and can access methods and the properties of the class.

Creating Objects in C#

In C#, once the class is defined in the program, we can easily create its object in the same manner that we define the variable of any other built-in data type. The object is created using the new keyword, which gives memory to the class and returns a reference to it.

Syntax:

It has the following syntax:

In this syntax,

• ClassName: It defines the name of the class.
• ObjectName: It refers to the name of the object of a class that can be created.
• new: The new keyword is used to make a new object in memory.

Let us take an example to define the object in C#.

Output:

Car Brand: Toyota
Manufacturing Year: 2022

Explanation:

In this example, we demonstrate how to use the object in C#. First, we create a class named Car. Inside the class, we create the method named ShowDetails().

In the main method, we create an object of the class Car. The brand and year of the item are given the values "Toyota" and 2022. Finally, we use the Console.WriteLine() function to print the output.

Characteristics of an Object

The several characteristics of an object are as follows:

• Identity: Every object has a unique identity, even if multiple objects have the same values for their properties.
• State: Data members of the class can represent the state of the object. It refers to the properties or data stored within the object.
• Behaviour: The behaviour of an object is represented as a data method of the class. It defines what operations the object can perform.

C# Classes and Objects Example

Let us take an instance of the class that contains two fields: id and name. We create an instance of the class and initialize the object, and then print the value.

Output:

501
Alex Parker

Explanation:

In this example, we demonstrate how to use the class and object in C#. First, we create a class named Worker that has two variables, WorkerId and WorkerName. After that, we create the object (w1) of the class (Worker) and assign the value 501 and Alex Parker. Finally, we use the Console.WriteLine() function to print the output.

Pass an Object as an Argument into a Method

In the C# programming language, we can pass an object to a method. The method is a code block that only runs when it is called and carries out a specific task. We can pass the data as arguments, and also pass an object as an argument that is an instance of a class.

When we pass an object to a method, the reference to the object is transmitted, and it doesn't create a copy of the object itself. Therefore, any changes made to the object inside the method will also affect the original object outside the method.

Syntax

It has the following syntax.

Let's take another example of a C# program where we store and retrieve employee information.

Output:

101  John  995000
102  Michael  29700

Explanation:

In this example, we define the class named Staff that contains the variables name, staff_id, staff_name, staff_salary, along with the method name ShowDetails(). After that, we create the objects (staff1, staff2) of the class (Staff) and assign the value. Finally, we are using the Console.WriteLine() function to print the output.

Differentiate between the Classes and Objects

Several differences between the classes and objects in C# are as follows.