Introduction to Polymorphism in C#

dept

Computer Science

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Introduction to Polymorphism in C#

• Polymorphism in C# enables the user to invoke a Child Class Method & override the Parent Class Method, using a Parent Class Reference variable.

• In our previous lecture on Inheritance, we have also discussed method hiding and our last code is shown in below figure:

• In the above code, you can see that we have used method hiding by using new keyword with ChildClass Method.
• So, now instead of hiding the method let's override it and have a look at the results:

• In the above figure, you can see that I have used virtual keyword with Parent Class Method.
• Moreover, instead of new keyword, I have used override keyword with Child Class Method.
• I have used the same reference variables as I did for Method Hiding code, but here in the third case, the child class method is called.
• So, in Polymorphism, if the Child Class is involved in reference variable, then it will always override the Parent Class Method and will use the Child Class Method.
• So, we can say that if we want to completely override any function in Parent Class, then we need to add virtual keyword in its definition.
• This virtual Parent Class Method will always get override by any Base Class Method, which has the same name and has override keyword in its definition.
• But if we want to invoke the virtual Parent Class Method, then we have to use Parent Class reference variable.
• So, this third variable PC2 is the main difference between Method Hiding & Method Overriding (Polymorphism).