Understanding class, object & interface
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The document provides an overview of classes, objects, and interfaces in C#, emphasizing their definitions, functionalities, and differences within object-oriented programming. It explains how classes act as blueprints for objects, which are instances of these classes, and details the role of interfaces in enforcing properties on object implementations. The document also touches upon member access modifiers, static members, and frequently asked questions about these concepts.
Understanding class, object & interface
- 1. Understanding Class, Object & Interface Md. Shohag Mia Software Developer (C#) shohag-ds@outlook.com
- 2. Contents Introductions Definition of Class, Object & Interface Adding variable & methods into Class Class member access modifiers & Constructor Creating objects & accessing class member Static Member for class Creating & Implement interface into class Distinguish between Class, Object & Interface Questions
- 3. Introduction Class & Object are the basic concepts of Object Oriented Programming which revolve around the real-life entities. In C#, classes support the polymorphism, inheritance and also provide the concept of derived classes and base classes. Interfaces in Object Oriented Programming Languages, An interface is a programming structure/syntax that allows the computer to enforce certain properties on an object (class).
- 4. Definition of Class Class: A class is like a blueprint of specific object. A class enables you to create your own custom types by grouping together variables of other types, properties, behavior, methods and events etc. Define an interface by using the class keyword. Example- Every object has some color, shape and functionalities etc. Syntax: public class MyClass { //Here are Properties, Methods & Events }
- 5. Definition of Object Object: An object is basically a block of memory that has been allocated and configured according to the blueprint of the class. A program may create many objects of the same class. Objects are also called instances and they can be stored in either a named variable or in an array or collection. Define an interface by using the new keyword. Example: Customer, Student, Mobile Phone & Car etc. Syntax: BankAccount account = new BankAccount()
- 6. Definition of Interface Interface: An interface is like an abstract base class. Any class or struct that implements the interface must implement all its members. An interface can't be instantiated directly. Its members are implemented by any class or struct that implements the interface. Interfaces can contain events, indexers, methods, and properties. Define an interface by using the interface keyword. Interfaces in C# are a means to get around the lack of multiple inheritance in C#, meaning you can’t inherit from multiple classes but you can implement multiple interfaces. Example: All bank account holders can be operate cash withdrawal & deposit commonly. Syntax: interface IMyInterface { // contain events, indexers, methods, and properties here… }
- 7. Adding variable/Properties & methods into Class
- 8. Class member access modifiers
- 9. Creating objects & accessing class member
- 10. Static Member for a class “static” means “relating to the type itself, rather than an instance of the type”. You access a static member using the type name instead of a reference or a value, e.g. DateTime.Now() In addition to methods and variables, you can also declare a class to be static (since C# 2.0). A static class cannot be instantiated and can only contain static members.
- 11. Creating & Implement interface into class
- 12. Distinguish between Class, Object & Interface Class Object Interface A class describes the attributes and behaviors (Blueprint) of an object. An object is the instance of the class to use variables and methods from inside the class. An interface contains behaviors that a derived class implements it. A class may contain abstract methods, concrete methods & constructor. A class may contain variables and methods. An interface contains only abstract methods & Doesn’t contains constructor. Members of a class can be public, private, protected or default. Internal is the default if no access modifier is specified. All the members of the interface are public by default. Classes have logical existence. Objects have a physical existence. Interface have logical existence. A class doesn't take any memory spaces when a programmer creates one. An object takes memory when a programmer creates one. A interface doesn't take any memory spaces but only for carry on reference. The class has to be declared only once. Objects can be declared several times depending on the requirement. The interface has to be declared only once.
- 13. Demo with Class
- 15. Try to Resolve What is class? What is object? What is interface? Difference between Class & Object? Difference between Class & Interface? Why we use static keyword? How static member is accessed? What is the benefits of interface? Can you explain about constructor & deconstructor? Can you create an instance of an interface? Can you create an instance of an abstract class? Why we can’t create an object of an abstract class? Why we can’t specify the accessibility modifier for methods inside the interface? Is it possible can have multiple methods in a single class? Is it necessary for abstract class to have abstract method? When do you favor abstract class over interface?
- 16. Any questions?