C# |继承

原文:https://www.geeksforgeeks.org/c-sharp-inheritance/

继承是面向对象编程的重要支柱。这是 C# 中允许一个类继承另一个类的特性(字段和方法)的机制。

重要术语:

  • 超类:特征被继承的类称为超类(或基类或父类)。
  • 子类:继承另一个类的类称为子类(或派生类、扩展类或子类)。除了超类字段和方法之外，子类还可以添加自己的字段和方法。
  • 可重用性:继承支持“可重用性”的概念，即当我们想要创建一个新的类，并且已经有一个类包含了我们想要的一些代码时，我们可以从现有的类中派生出我们的新类。通过这样做，我们重用了现有类的字段和方法。

如何使用继承

用于继承的符号为 : 。 语法:

class derived-class : base-class  
{  
   // methods and fields  
   .
   .
}

示例:在下面的继承示例中，类 GFG 是基类，类 GeeksforGeeks 是扩展 GFG 类的派生类，类 Sudo 是运行程序的驱动类。

// C# program to illustrate the
// concept of inheritance
using System;
namespace ConsoleApplication1 {

// Base class
class GFG {

   // data members
    public string name;
    public string subject;

    // public method of base class 
    public void readers(string name, string subject)
    {
        this.name = name;
        this.subject = subject;
        Console.WriteLine("Myself: " + name); 
        Console.WriteLine("My Favorite Subject is: " + subject);
    }
}

// inheriting the GFG class using : 
class GeeksforGeeks : GFG {

    // constructor of derived class
    public GeeksforGeeks()
    {
        Console.WriteLine("GeeksforGeeks");
    }
}

// Driver class
class Sudo {

    // Main Method
    static void Main(string[] args)
    {

        // creating object of derived class
        GeeksforGeeks g = new GeeksforGeeks();

        // calling the method of base class 
        // using the derived class object
        g.readers("Kirti", "C#");
    }
}
}

输出:

GeeksforGeeks
Myself: Kirti
My Favorite Subject is: C#

c# 中的遗传类型

下面是 C# 在不同组合中支持的不同类型的继承。

  1. Single Inheritance: In single inheritance, subclasses inherit the features of one superclass. In image below, the class A serves as a base class for the derived class B.

  2. Multilevel Inheritance: In Multilevel Inheritance, a derived class will be inheriting a base class and as well as the derived class also act as the base class to other class. In below image, class A serves as a base class for the derived class B, which in turn serves as a base class for the derived class C.

  3. Hierarchical Inheritance: In Hierarchical Inheritance, one class serves as a superclass (base class) for more than one subclass. In below image, class A serves as a base class for the derived class B, C, and D.

  4. Multiple Inheritance(Through Interfaces):In Multiple inheritance, one class can have more than one superclass and inherit features from all parent classes. Please note that C# does not support multiple inheritance with classes. In C#, we can achieve multiple inheritance only through Interfaces. In the image below, Class C is derived from interface A and B.

  5. Hybrid Inheritance(Through Interfaces): It is a mix of two or more of the above types of inheritance. Since C# doesn’t support multiple inheritance with classes, the hybrid inheritance is also not possible with classes. In C#, we can achieve hybrid inheritance only through Interfaces.

c# 中关于继承的重要事实

  • 默认超类:除了 Object 类没有超类之外，每个类都有且只有一个直接超类(单继承)。在没有任何其他显式超类的情况下，每个类都隐式地是对象类的子类。
  • 超类只能是一个:超类可以有任意数量的子类。但是一个子类只能有一个超类。这是因为 C# 不支持类的多重继承。虽然有接口，但是 C# 支持多重继承。
  • 继承构造函数:子类从其超类继承所有成员(字段、方法)。构造函数不是成员，所以它们不会被子类继承，但是超类的构造函数可以从子类中调用。
  • 私有成员继承:子类不继承其父类的私有成员。但是，如果超类具有用于访问其私有字段的属性(get 和 set 方法)，那么子类可以继承。

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