oops concept c#

First of all here is a tip, the concept is not OOPS, it is OOP; Object-oriented programming. OOPS does not exist. :-)

Secondly, the inheritance that you are talking about (as you are talking) is not able to be implemented. Why? Because a parent cannot call the functions of a child object. A child has ability to call the function of a parent class. That is the basic fundamental concept of inheritance. Let us see, how,

class Father 
{
   public void SayHello() { Console.WriteLine("Hello"); }
} 
 
class Son : Father
{
   // SayHello exists
   public void SayBye() { Console.WriteLine("Catch you later!"); }
}

Now, in the above inheritance, you see that Son has the SayHello function but it does also hold a definition for SayBye function. Why? Because of inheritance, a derived class can for sure inherit the functions of base class, but at the same time it can create more distinct functions in it also; for example SayBye.

new Father().SayBye(); // Doesn't work
new Son().SayHello(); // Works; inheritance 
new Son().SayBye(); // Works

If you try to call it on Father, that won't work because Father doesn't contain a definition for SayBye, inheritance works from Top-bottom (Father-to-Son) not the other way around. So, that is the problem.

However, if you cast the Father to Son, it would be able to call the function again as if it were defined as a Son object. :-)

(new Father() as Son).SayBye(); // Works;

But the sad side is that it will cause a NullReferenceException because Son is not yet instantiated.

2 Replies

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Afzaal Ahmad Zeeshan11y ago
First of all here is a tip, the concept is not OOPS, it is OOP; Object-oriented programming. OOPS does not exist. :-)

Secondly, the inheritance that you are talking about (as you are talking) is not able to be implemented. Why? Because a parent cannot call the functions of a child object. A child has ability to call the function of a parent class. That is the basic fundamental concept of inheritance. Let us see, how,
```
class Father 
{
   public void SayHello() { Console.WriteLine("Hello"); }
} 
 
class Son : Father
{
   // SayHello exists
   public void SayBye() { Console.WriteLine("Catch you later!"); }
} 
```
Now, in the above inheritance, you see that Son has the SayHello function but it does also hold a definition for SayBye function. Why? Because of inheritance, a derived class can for sure inherit the functions of base class, but at the same time it can create more distinct functions in it also; for example SayBye.
```
new Father().SayBye(); // Doesn't work
new Son().SayHello(); // Works; inheritance 
new Son().SayBye(); // Works 
```
If you try to call it on Father, that won't work because Father doesn't contain a definition for SayBye, inheritance works from Top-bottom (Father-to-Son) not the other way around. So, that is the problem.

However, if you cast the Father to Son, it would be able to call the function again as if it were defined as a Son object. :-)
```
(new Father() as Son).SayBye(); // Works;
```
But the sad side is that it will cause a NullReferenceException because Son is not yet instantiated.
Harshad Pansuriya11y ago
Hi Ashutosh,

Please Refer This Link You have idea given Here : OOps Concept in c#