OOP (object oriented programming)What is the class?What do you mean by object?What are the differences between class and object?Can you create an object without using new operator in C#?What is constructor and how many constructors can have one class?Differences between constructor and method of the class? What is default constructor?What is parameterized Constructor in C#?What is private constructor: In what instances you will declare a constructor to be private?What is static constructor, Is it possible to have a static constructor in class. If yes why we need to have a static constructor?Does C# provide copy constructor for an object? How do you call the multiple constructors of a class with single object creation?What is constructor chaining in C#?Can a constructor be called directly from a method?What is constructor overloading and how it’s different than method overloading?What is the difference between constructor overloading and method overloading?Is it possible to overload copy constructor in C#?Can we overload static constructors in C#?Can we overload private constructors in C#?Can we give return type of the constructor in C#?What is the destructor and when it’s called?Is it possible to call constructor and destructor explicitly?What is the Structure and why we need it although we have a class?What are the similarities between Class and Structure?What is the difference between Class and Structure?What is copy structure?What is nested structure?Is it always necessary to create an object of the class?How many different ways to create an object of the class?What are the pros and cons of creating object by new() keyword?What are the pros and cons of delegate object creation to DI container?What are the pros and cons of creating an object by reflection?What are the pros and cons of getting an object from an object pool?What are the pros and cons of creating an object by deserialization?Is it possible to create an object without a class in C#?What is constant?What is static modifier? What are the Static fields and methodsWhat is Static ReadOnly?What are the limitations of static?What is readonly? What’s the difference between constant and read-only?What is this keyword?What is base keyword?What is the difference between this and base keyword?Can “this” keyword be used within static method?What are the accessors?What is the static class? Why we need of static class?If someone wants to create static class then what are the rules for the static class?What are the limitations of using static keyword?What are finalizers in c#?How to create N number of instances of C# class?What are the Nested Classes and why we use them?What are the basic four pillars of OOP?What is the Inheritance and why we need of inheritance?How do you inherit a class into other class in C#?What is the concept of base and derive class?What are the different types of inheritance?We have two classes’ base class and child class. A is the base class and B is the child class, If we create an instance of child class then which class’s constructor called first?Does a derived class can inherit the constructors of its base class?What should we do that if we create an object of child class then the parameterized constructor of base class must be invoked?As we know that base constructor invoked first when we create instance of child class but if we create an instance of child class by parameterized constructor and base class has both default and parameterized constructor then which constructor of the base will be invoked?Can you assign an object of derived class to the variable of base class and if both have the same method name then which will be invoked?Can we create instance of base class and store it to derive class?Can we create derive class object inside base class, and if create instance of child class then what will happen?Can we inherit child class from 2 base classes? if yes then how? If not then why?Does C# support Multiple Inheritance?Why multiple inheritance is not supported in C# and why it’s supported in C++?How is multiple inheritance achieved in C#?What are Access Modifiers? Explain private, public, protected, internal, protected internal access modifiersWhat are the default access modifiers of the class?Why classes cannot be declared as protected?Can we declare private class in namespace?What are the valid access specifier used for the declaration of class at namespace level? If we inherit a class, do the private variables also get inherited?Can you prevent your class from being inherited?Can you prevent your class from being inherited without using sealed keyword?What is abstraction?What is encapsulation?What is the difference between abstraction and encapsulation?What is polymorphism?What is static or compile time polymorphism?What is runtime polymorphism or late binding or dynamic binding?What is method overloading?When and why we should use overload methods?What is inheritance based overloading?What are the advantages of using overloading?Can we overload the method in the same class?What is the execution control flow in overloaded methods?What is method overriding?What s virtual keyword?What are the key points to make the method as overridden?When it is must to override the method?When a derived class can overrides the base class member?Can we declare fields inside the class as virtual?When we treat sub-class method as an overriding method?Can we override private virtual method in c#?Can we override method in the same class?Can we execute parent class method if it is overridden in the child class?If we have virtual in base class and the same method is overridden in child class, by creating instance of child class and assign it to base class, then which of the method will be invoked first.What is the difference between method overloading and method overriding?What is method hiding?Can you access a hidden method in the derived which is declared in the base class?What is the difference between method overriding and method hiding?You have a component with 2 parameters and deployed to client side, now you have changed your method with 3 parameters, how can you deploy this without affecting the client code?What is operator overloading?What is abstract class and why we need of it?What are the rules of abstract classes?What is an abstract method?What is concrete method?When do you use abstract class in C#?When to use the abstract method in C#?

What is the Inheritance and why we need of inheritance?

Inheritance is like sharing and passing down traits from one thing to another. Imagine you have a toy robot with cool features. Now, you want to make a new robot that's similar to the first one, but with a few extra tricks. Instead of building everything from scratch, you can use inheritance.

In programming, inheritance is when you create a new class based on an existing class. This new class gets all the qualities of the old one, plus you can add or change things to make it special.

Imagine you have a "Vehicle" class that has properties like speed and color. Now you want to make a "Car" class. Instead of rewriting all the speed and color stuff, you can inherit from the "Vehicle" class. This means the "Car" class automatically has speed and color, and you can add more car-specific things to it.

Inheritance makes programming faster and organized. It helps you reuse code and build new things on top of existing things. Just like building a new robot that's awesome by starting with the cool features of the old one.

Here are some points to remember about inheritance in C#:
  • Inheritance is the important pillar of object oriented programming in which one class inherits the features of another class to access the members (properties and methods) of other class.
  • The class which is inherited by another class is called super class, base class or parent class.
  • The class which inherits the other class is known as sub class or derived class or extended class or child class.
  • The derived class is allowed to add its own field and methods in addition of super class.
  • In C#, colon (':') is the symbol used for inheritance.

The inheritance implements the IS-A relationship. For example 'Mammal' is a animal. 'Sheep' IS A mammal, hence sheep is also an animal. Let's illustrate inheritance with an example using classes related to animals:

using System;

// Base class: Mammal
class Mammal
    public void Breathe()
        Console.WriteLine("Mammal is breathing");

// Derived class: Animal (inherits from Mammal)
class Animal : Mammal
    public void Move()
        Console.WriteLine("Animal is moving");

// Further derived class: Sheep (inherits from Animal)
class Sheep : Animal
    public void Bleat()
        Console.WriteLine("Sheep is bleating");

class Program
    static void Main(string[] args)
        // Create an instance of Sheep
        Sheep mySheep = new Sheep();

        // Use methods from different levels of inheritance
        mySheep.Breathe();  // Method from Mammal
        mySheep.Move();     // Method from Animal
        mySheep.Bleat();    // Method from Sheep

In this example:

  • 'Mammal' is the base class. It has a method 'Breathe()'.
  • 'Animal' is derived from 'Mammal'. It has a method 'Move()' and inherits the 'Breathe()' method from 'Mammal'.
  • 'Sheep' is further derived from 'Animal'. It has a method 'Bleat()' and inherits both the 'Move()' and 'Breathe()' methods from its parent classes.

When you create an instance of 'Sheep' and call methods on it, you can see how the inheritance works:

  • The 'Breathe()' method is inherited from 'Mammal'.
  • The 'Move()' method is inherited from 'Animal'.
  • The 'Bleat()' method is specific to the 'Sheep' class.

This way, you can see how the traits and behaviors of each class are inherited and built upon as you move down the inheritance hierarchy.

Why we use inheritance?

Inheritance is like sharing good stuff between classes. Imagine you're making a new app, and you need a class that does some things. But there's already a class that does similar things. Instead of making everything from scratch, you can use the old class as a starting point by inheriting from it. The old class is like a helpful friend, and your new class is like you learning from that friend.

This also makes things quicker because you don't need to write as much code. The old class already has some cool stuff, so you just need to add a little bit to make it do exactly what you want. It's like starting with a recipe that's almost perfect and just adding your secret ingredient.