Inheritance and Interfaces

• Inheritance


  Allows the defining of a child class that reuses or inherits the behavior of a parent class (or existing class).
• The inheriting class is called a derived class or subclass
• The existing class whose members are being inherited is called base class or superclass.
• Subclass can only inherit from a single superclass.
• The colon (:) symbol indicates that the class DerivedClass inherits the members of the class BaseClass.
• protected members of a base class are inherited and are accessible by their derived classes.
• The keyword protected is used to declare a protected member.
• base keyword is used to specify which constructor from the base class should invoke when creating instances of the derived class.
• Declaring a method in a derived class with the same name as the method from its base class is called method overriding.
• Method overriding is redefining the functionality of an existing method.
• The overridden method from the base class should be declared as virtual
• The virtual modifier specifies that a derived class can override the method in the base class.
• The override modifier is required to modify the abstract or virtual implementation of the inherited method and must have the same method signature as the overridden method (virtual method).
• Only an abstract and virtual method can be overridden in C#.
• Abstract class is a base class that cannot be instantiated to create an object.
• The abstract keyword is used to declare an abstract class and is placed before the class name.
• Polymorphism, which means “multiple forms,” is one of the fundamental concepts of object-oriented programming.
• POLYMORPHISM enables classes to provide multiple methods with the same name but with different implementations or behavior.
• Compile time polymorphism – Also known as “static polymorphism,”
• Compile time polymorphism is implemented using method overloading. In method overloading, a method is executed depending on the number and type of parameters passed to it.
• Runtime polymorphism – This polymorphism is a process in which the compiler determines which method to call during runtime.
• Runtime process is also called dynamic polymorphism or late binding. This is achieved using method overriding.
• An interface only contains the signatures of methods, properties, and events as its members.
• Interfaces are not classes. In C#, interfaces are defined using the interface keyword.
• A property can access a private data member of the class.
• An interface cannot contain instance variables or fields but may contain properties.