Chapter 3 C # basic learning 3

2.2.6 inheritance and Methods

Inheritance changes the methods for declaring and calling methods. When a subclass is derived from a base class, inheritance is useful for subclasses to implement and redefine existing methods in the base class.

2.2.6.1 abstract Method

Abstract methods are useful when a base class cannot provide any meaningful implementation for a method.

Override keyword.

2.2.6.2 virtual Method

Using the abstract keyword base class requires that its derived class must implement a certain method.

Use the virtual keyword, which is allowed but does not require a base (derived class ?) Class provides a new implementation.

New Keyword, which can be used to hide basic class virtual methods.

2.2.7 accessibility

For class members, there are 5 accessible levels:

Public is fully open and accessible

Protected can only access the classes and their subclasses that encapsulate this member.

Internal can only accessProgramClass inside the set

Protected internal allows you to access the classes inside the Assembly that encapsulates the Member, encapsulate the member classes and their subclasses.

Private class with full access to encapsulate this Member

2.2.7.1 data type accessibility options

Interface member and enumeration type

Structure Member

Class Member

Accessible nesting

2.2.7.2 allow access to known friends