面向对象编程中最重要的概念之一是继承,继承允许我们根据另一个类来定义类,这使得创建和维护应用程序变得更加容易。这也提供了重用代码功能的机会,并加快了实现时间。
一个类可以从多个类或接口继承,这意味着它可以从多个基类或接口继承数据和函数。
C#中用于创建继承类的语法如下所示:-
<acess-specifier> class <base_class> { ... } class <derived_class> : <base_class> { ... }
考虑基类Shape及其继承类Rectangle-
using System; namespace InheritanceApplication { class Shape { public void setWidth(int w) { width = w; } public void setHeight(int h) { height = h; } protected int width; protected int height; } //Derived class class Rectangle: Shape { public int getArea() { return (width * height); } } class RectangleTester { static void Main(string[] args) { Rectangle Rect = new Rectangle(); Rect.setWidth(5); Rect.setHeight(7); //Print the area of the object. Console.WriteLine("Total area: {0}", Rect.getArea()); Console.ReadKey(); } } }
编译并执行上述代码时,将生成以下输出-
Total area: 35
继承类继承基类变量和方法,因此,应该在创建子类之前创建超类对象,您可以在初始化列表中提供超类初始化的说明。
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using System; namespace RectangleApplication { class Rectangle { //member variables protected double length; protected double width; public Rectangle(double l, double w) { length = l; width = w; } public double GetArea() { return length * width; } public void Display() { Console.WriteLine("Length: {0}", length); Console.WriteLine("Width: {0}", width); Console.WriteLine("Area: {0}", GetArea()); } }//end class Rectangle class Tabletop : Rectangle { private double cost; public Tabletop(double l, double w) : base(l, w) { } public double GetCost() { double cost; cost = GetArea() * 70; return cost; } public void Display() { base.Display(); Console.WriteLine("Cost: {0}", GetCost()); } } class ExecuteRectangle { static void Main(string[] args) { Tabletop t = new Tabletop(4.5, 7.5); t.Display(); Console.ReadLine(); } } }
编译并执行上述代码时,将生成以下输出-
Length: 4.5 Width: 7.5 Area: 33.75 Cost: 2362.5
C#不支持多重继承,但是,您可以使用接口来实现多重继承,以下程序演示了此-
using System; namespace InheritanceApplication { class Shape { public void setWidth(int w) { width = w; } public void setHeight(int h) { height = h; } protected int width; protected int height; } //Base class PaintCost public interface PaintCost { int getCost(int area); } //Derived class class Rectangle : Shape, PaintCost { public int getArea() { return (width * height); } public int getCost(int area) { return area * 70; } } class RectangleTester { static void Main(string[] args) { Rectangle Rect = new Rectangle(); int area; Rect.setWidth(5); Rect.setHeight(7); area = Rect.getArea(); //Print the area of the object. Console.WriteLine("Total area: {0}", Rect.getArea()); Console.WriteLine("Total paint cost: ${0}" , Rect.getCost(area)); Console.ReadKey(); } } }
编译并执行上述代码时,将生成以下输出-
Total area: 35 Total paint cost: $2450
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