OOP polymorphism and Inheritance essentials

Early binding and polymorphism

• The signature rules for C # function overloading are judged by the type and number of arguments, not by the name of the function.
• The function return value is not signed as an overload.
• Modifiers are not part of a signature, such as static
• In the same function, multiple parameter names are unique
• Ref, Out is a reference pass, the memory address of the parameter is passed
• Params as a parameter key, can only be used for the last parameter of a function

Inherited

• Cannot prevent subclasses from overriding the base-like signature method
• An inheritance relationship is a subclass of the same signature method that looks up first, then finds its base class
• The base keyword is used by C # to call base class functions, variables in subclasses
• The inheritance relationship is irreversible
• In addition to constructors and destructors, subclasses inherit some of the base class
• Custom classes inherit from the object type by default, but these types of C # cannot be inherited:,,, System.ValueType System.Enum System.Delegate System.Array , etc.
• C # does not support inheriting from multiple classes
• C # does not support circular inheritance
• Sub-class objects can be assigned directly to the base class, whereas a strong turn is required

Virtual

• In C #, a subclass object can be assigned to a base class object, whereas a strong turn is required.
• The override keyword is used for subclasses overriding the same signature as the base class virtual function
• Use new and override to override the same signature function of the base class virtual
• A function of the virtual modifier that can only be executed at run time
• function is not modified by virtual, it can be determined at compile time whether it is called

Abstract classes and abstract methods

• Unable to instantiate with newabstract 抽象类
• abstract 抽象类可以有子类，其子类实现抽象方法后，可被new实例化对象
• 如声明了abstract 的函数，则必须声明abstract 的类
• 当override抽象基类，无法修改基类函数的签名
• abstract函数，无法同时添加static、virtual关键字
• abstract 类无法被声明为sealed、static类

OOP polymorphism and Inheritance essentials