Why oops in net

A class has different members, and developers in Microsoft suggest to program them in the following order:. Access keywords define the access to class members from the same class and from other classes. The most common access keywords are:. Objects are the building blocks of OOP and are commonly defined as variables or data structures that encapsulate behavior and data in a programmed unit.

Objects are items that can be individually created, manipulated, and represent real world things in an abstract way. Not everything in the real world should be represented as a class.

Structures are suitable to represent lightweight objects. Structures can have methods and properties and are useful for defining types that act as user-defined primitives, but contain arbitrary composite fields.

NET Framework defines some structures such as System. Rectangle, System. Point, and System. OOP is full of abstract concepts, and the best approach to understand them is practical and not only theoretical. I learned more OOP after making some designs and after implementing some components. The concepts presented in this article might clarify the meaning, but I strongly recommend to go and have fun playing around with OOP. In this article, I examined the concept of classes, objects, and structs.

View All. Public class ChildClass : BaseClass. Public ChildClass. WriteLine "Child Class Constructor executed" ;. Public static void Main. Write ;. In the Main method in ChildClass we create an instance of childclass. Then we call the write method. If you observe the ChildClass does not have a write method in it. This write method has been inherited from the parent BaseClass. The output of the above program is Output:.

So in general Base classes are automatically instantiated before derived classes. The base class is specified by adding a colon, ":", after the derived class identifier and then specifying the base class name. C supports single class inheritance only. What this means is, your class can inherit from only one base class at a time. In the code snippet below, class C is trying to inherit from Class A and B at the same time.

This is not allowed in C. This will lead to a compile time. In C Multi-Level inheritance is possible. Code snippet below demonstrates mlti-level inheritance. Class B is derived from Class A. Class C is derived from Class B. Note: Classes can inherit from multiple interfaces at the same time. Interview Question: How can you implement multiple inheritance in C? Ans : Using Interfaces. We will talk about interfaces in our later article.

Public class A. Public class B : A. Public class C : B. When you derive a class from a base class, the derived class will inherit all members of the base class except constructors. In the code snippet below class B will inherit both M1 and M2 from Class A, but you cannot access M2 because of the private access modifier.

Class members declared with a private access modifier can be accessed only with in the class. We will talk about access modifiers in our later article. Common Interview Question : Are private class members inherited to the derived class?

Ans: Yes, the private members are also inherited in the derived class but we will not be able to access them.

Trying to access a private base class member in the derived class will report a compile time error. Public void M1. Private void M2. Method Hiding and Inheritance We will look at an example of how to hide a method in C. The Parent class has a write method which is available to the child class. In the child class I have created a new write method. So, now if I create an instance of child class and call the write method, the child class write method will be called.

The child class is hiding the base class write method. This is called method hiding. If we want to call the parent class write method, we would have to type cast the child object to Parent type and then call the write method as shown in the code snippet below. Public class Parent. WriteLine "Parent Class write method" ;.

Hence, you gain re-usability by means of four main object-oriented programming concepts. Below are object oriented programming concepts : Object Object is representative of the class and is responsible for memory allocation of its data members and member functions.

An object is a real world entity having attributes data type and behaviors functions. An object can be considered a "thing" that can perform a set of related activities. The set of activities that the object performs defines the object behavior. For example, the hand can grip something or a Student object can give the name or address Class Class is a data structure that contains data members constants files, events , member function methods, properties, constructor, destructor, indexers and nested type.

Basically It is a user defined data type. It is a reference type. Infact class is a tag or template for object. Encapsulation provides a way for abstraction. In OOP the encapsulation is mainly achieved by creating classes, the classes expose public methods and properties. The class is kind of a container or capsule or a cell, which encapsulate the set of methods, attribute and properties to provide its indented functionalities to other classes. Data abstraction Data abstraction is a mechanism to provide the essential features without describing the background details.

Accessibility sets the visibility of the member to outside assemblies or derived types. The following table describes member accessibility;. Constructors in a base class are not inherited in a derived class. A derived class has a base portion and derived portion. The base portion initializes the base portion, and the constructor of the derived class initializes the derived portion. So the base keyword refers to the base class constructor, while parameterlist2 determines which overloaded base class constructor is called.

In the following example, the Child class's constructor calls the single-argument constructor of the base Father class;. At line 4, we are defining a base Father Class constructor and in the derived class Child, at line 8 we are initializing it explicitly via base keyword. If we pass any parameter in the base class constructor then we have to provide them in the base block of the child class constructor.

By declaring a base class function as virtual, you allow the function to be overridden in any derived class. The idea behind a virtual function is to redefine the implementation of the base class method in the derived class as required.

If a method is virtual in the base class then we have to provide the override keyword in the derived class. Neither member fields nor static functions can be declared as virtual. If a method with the same signature is declared in both base and derived classes, but the methods are not declared as virtual and overriden respectively, then the derived class version is said to hide the base class version. In most cases, you would want to override methods rather than hide them.

NET automatically generates a warning. In the following example, we are defining a VirutalMethod in the myBase class but not overriding it in the derived class, so in that case the compiler will generate a warning. The compiler will assume that you are hiding the base class method.

So to overcome that problem, if you prefix the new keyword in the derived class method then the compiler will prefer the most derived version method. You can still access the base class method in the derived class by using the base keyword. C allows both classes and functions to be declared abstract using the abstract keyword. You can't create an instance of an abstract class.

An abstract member has a signature but no function body and they must be overridden in any non-abstract derived class. Abstract classes exist primarily for inheritance. Member functions, properties and indexers can be abstract.

A class with one or more abstract members must be abstract as well. Static members can't be abstract. In this example, we are declaring an abstract class Employess with a method displayData that does not have an implementation.

Then we are implementing the displayData body in the derived class. One point to be noted here is that we have to prefixe the abstract method with the override keyword in the derived class.

Sealed classes are the reverse of abstract classes. While abstract classes are inherited and are refined in the derived class, sealed classes cannot be inherited.

You can create an instance of a sealed class. A sealed class is used to prevent further refinement through inheritance. Suppose you are a developer of a class library and some of the classes in the class library are extensible but other classes are not extensible so in that case those classes are marked as sealed. An interface is a set of related functions that must be implemented in a derived class.

Members of an interface are implicitly public and abstract. Interfaces are similar to abstract classes. First, both types must be inherited; second, you cannot create an instance of either. Although there are several differences as in the following;. So the question is, which of these to choose?

Select interfaces because with an interface, the derived type still can inherit from another type and interfaces are more straightforward than abstract classes. Polymorphism is the ability to treat the various objects in the same manner. It is one of the significant benefits of inheritance. We can decide the correct call at runtime based on the derived type of the base reference. This is called late binding.

In the following example, instead of having a separate routine for the hrDepart, itDepart and financeDepart classes, we can write a generic algorithm that uses the base type functions. The method LeaderName declared in the base abstract class is redefined as per our needs in 2 different classes.

View All. Object Oriented Programming Using C. Vidya Vrat Agarwal Updated date Nov 01, This chapter covers the following: OOP's overview Classes and Objects Constructor and Destructor Function Overloading Encapsulation Inheritance Interface Polymorphism Encapsulation Encapsulation binds together code and the data it manipulates and keeps them both safe from outside interference and misuse. Inheritance Inheritance is the process by which one object acquires the properties of another object.

Polymorphism Polymorphism is a feature that allows one interface to be used for a general class of action. Reusability Once a class has been written, created and debugged, it can be distributed to other programmers for use in their own program. Simple "Hello World" C Program This simple one-class console "Hello world" program demonstrates many fundamental concepts throughout this article and several future articles.

WriteLine "Hello World! Compiling the Program You can compile a C program into either an assembly or a module. The following table lists the accessibility keywords; Keyword Description public Public class is visible in the current and referencing assembly. Internal Visible inside containing assembly.

Internal protected Visible inside containing assembly and descendent of thecurrent class. The list of all modifiers defined in the table are as follows; Modifier Description sealed Class can't be inherited by a derived class. Abstract The instance of the class is not created if the Class is abstract. Then in the Solution Explorer, you will notice some files that are automatically created as, You can also write your own code in the default program. Give the name to the class "customer" as in the following; When you open the customer.

Generic; using System. Linq; using System. WriteLine obj. CustID ; Console.