C# Class and Objects

Classes and Objects in C#

• C# is an object-oriented programming language where everything is associated with classes and objects, along with their attributes and methods.
• A class is a user-defined blueprint or prototype from which objects are created.
• An object is the basic unit of Object Oriented Programming and represents real-life entities.
• Before creating an object, we first need to define the class.

Creating a Class and Object

• To create a class, use the keyword class.
• To create an object of a class, use the new keyword.

Multiple Objects

• You can create multiple objects of one class.
• Each object has its own set of attributes and methods.

Using Multiple Classes

• You can create an object of a class and access it in another class.
• This is used for better organization of classes.

Class Attributes

• Class attributes are variables within a class.
• Attributes can be declared as public or private.

Accessing Attributes

• You can access attributes by creating an object of the class and using the dot syntax (.).
• Example: myObj.x to access the x attribute of the myObj object.

Modify Attributes

• You can modify attribute values.
• Example: myObj.x = 40 to set the value of x to 40.

Multiple Attributes

• You can specify as many attributes as you want.

Multiple Objects with Attributes

• If you create multiple objects of one class, you can change the attribute values in one object without affecting the attribute values in the other.

Final Keyword

• The final keyword is used to declare an attribute that cannot be overridden.
• Example: public final double PI = 3.14159;

Static Keyword

• The static keyword is a non-access modifier used for methods and attributes.
• A static method or attribute can be accessed without creating an object of the class.

Homework

• Write a C# program to create a class called "Rectangle" with width and height attributes.
• Calculate the area and perimeter of the rectangle in two different methods.
• Create a simple application for managing student information.
• Create a simple application to manage employees' information in a company.

Classes and Objects

• C# is an object-oriented programming language.
• Everything in C# is associated with classes and objects, along with their attributes and methods.
• A class is a user-defined blueprint or prototype from which objects are created.
• An object is the basic unit of Object-Oriented Programming and represents real-life entities.

Creating a Class and Object

• To create a class, use the keyword class.
• To create an object of a class, use the class name followed by the object name.
• Example: Main myObj = new Main();

Multiple Objects

• You can create multiple objects of one class.
• Each object has its own set of attributes and values.

Using Multiple Classes

• You can create an object of a class and access it in another class.
• This is useful for better organization of classes.

Class Attributes

• Class attributes are variables within a class.
• Example: class Main { int x; int y; }

Accessing Attributes

• You can access attributes by creating an object of the class and using the dot syntax (.`).
• Example: Main myObj = new Main(); Console.WriteLine(myObj.x);

Modifying Attributes

• You can modify attribute values.
• Example: Main myObj = new Main(); myObj.x = 40;

Multiple Attributes

• You can specify as many attributes as you want.
• Example: class Main { int x; int y; int z; }

Multiple Objects and Attributes

• If you create multiple objects of one class, you can change the attribute values in one object without affecting the other objects.
• Example: Main myObj1 = new Main(); Main myObj2 = new Main(); myObj2.x = 25;

Final Keyword

• The final keyword is used to prevent the override of existing values.
• Example: final int PI = 3.14159;

Static Keyword

• The static keyword is a non-access modifier used for methods and attributes.
• A static method or attribute can be accessed without creating an object of the class.
• Example: class Example { static int age = 20; public static void print() { ... } }

Homework

• Write a C# program to create a class called "Rectangle" with width and height attributes, and calculate the area and perimeter of the rectangle in two different methods.
• Create a simple application for managing student information, where each student is represented as an object with properties such as name, age, and student ID.