Class and Object in C#

 

Class :

 

v Class is a collection of variables, constants, methods, properties and constructors etc.  These all are called members of class.

 

v class keyword in used to create a class in C#.

 

v Classes are reference types that hold the object created dynamically in a heap.

 

v Classes are the user defined data types that represent the state and behaviour of an object. State means properties or data and behaviour means functionality that objects can perform.

 

v The default access modifier of a class is Internal.

 

v The default access modifier of class members is Private.

 

v To access the class members, you use the dot (.) operator.

 

v The dot operator links the name of an object with the name of a member.

 

 

 

 

 

 

 

 

 

 

The syntax of a class definition is given as follows:

 

AccessSpecifier class NameOfClass

{

  Class members like   variables/ functions/methods/properties etc.

}     

 

  

For example:

public class Students

{

int id=100;

string name;

}

Here,

 

public - access specifier/modifier.

 

class - reserved keyword.

 

Students – User define class name.

 

Id, name – variables.

 

100 = constant.

 

 

 

Object:

v In C#, Object is a real world entity, for example, chair, car, pen, mobile, laptop etc.

 

v Object is an entity that has state and behaviour. Here, state means data and behaviour means functionality.

 

v Object is a runtime entity, it is created at runtime.

 

v A program may create many objects of the same class.

v Objects are also called instances, and they can be stored in either a named variable or in an array or collection.

 

v Object is an instance of a class. All the members of the class can be accessed through object.

 

v In C#, an object of a class can be created using the new keyword and assign that object to a variable of a class type.

 

Example: Create an Object of a Class

Student myStudent = new Student();

Here we have created an instance of class “Student” and we have defined “myStudent” variable as a reference object and The new keyword allocates memory at runtime.

 

You can now access public members of a class using the object.MemberName notation.

 

 

 

Example: Access Members of a Class

Student mystudent = new Student();

mystudent.FirstName = "Steve";

mystudent.LastName = "Jobs";

 

You can create multiple objects of a class with different values of properties and fields.

 

Example: Create Multiple Objects of a Class

Student mystudent1 = new Student();

mystudent1.FirstName = "Steve";

mystudent1.LastName = "Jobs";

 

Student mystudent2 = new Student();

mystudent2.FirstName = "Bill";

mystudent2.LastName = "Gates";

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Advantages of Objects and Classes:

1.   Objects and classes help us to divide a large project into smaller sub-problems.

 

2.   This helps to manage complexity as well as make our code reusable.

 

Suppose you want to create a game that has hundreds of enemies and each of them has fields like health, and methods like shoot () and run ().

 

With C# we can create a single Enemy class with required fields and methods. Then, we can create multiple enemy objects from it.

 

Each of the enemy objects will have its own version of health and ammo fields. And, they can use the common shoot() and run() methods.

 

Now, instead of thinking of projects in terms of variables and methods, we can think of them in terms of objects.

 

 

 

 

 

 

 

 

 

 

Real Life Examples:

v Class is the blueprint for the object. Class as a sketch (prototype) of a house. It contains all the details about the floors, doors, windows, etc. We can build a house based on these descriptions. House is the object.

 

v Like many houses can be made from the sketch, we can create many objects from a class.

 

 

v If animal is the class then dog, tiger, lion and elephant etc. is the object.

 

v If human is the class then man and women is the object.

 

v A dog has legs and eyes, then eyes is the variable in the technical concept, this is the property and the dog may run or may walk, these are methods.

 

v A car is an object. The car has attributes, such as weight and colour, and methods, such as drive and break.