C# 简单的运用继承 方法重写 字段公有化

using System;
using System.Collections.Generic;
using System.Text;

namespace HELLO
{
    class 矩形
    {
        static void Main(string[] args)
        {
            Line line = new Line();//实例化
            line.widthcalue = 8;//属性赋值
            line.lengthvalue = 9;//属性赋值
            double area = line.area1();
            Console.WriteLine("长方形的面积是{0}", area);
            line.setlength(4);
            line.setwidth(5);
            double area1 = line.area1();
            Console.WriteLine("长方形的面积是{0}", area1);
            Line1 line1 = new Line1();
            line1.setlength(3);
            line1.setwidth(2);
            Console.WriteLine("长方形的面积是{0}", line1.area1()); ;
        }
        class Line
        {
            internal double length, width;//私有字段，外部访问不到
            public void setlength(double a) { length = a; } //通过公有的方法赋值私有字段
            public void setwidth(double b) { width = b; }//通过公有的方法赋值私有字段
            public double widthcalue { set { width = value; } get { return width; } }//属性赋值私有字段
            public double lengthvalue { set { length = value; } get { return length; } }//属性赋值私有字段
            public double area1() { return length * width; }//根据字段值计算
        }
        class Line1 : Line //继承
        {
            public new void setlength(double a) { length = a * 2; } //重写普通公有的方法赋值私有字段
            public new void setwidth(double b) { width = b * 2; }//重写普通公有的方法赋值私有字段
            public new double area1() { return length * width * 2; }//重写返回值
        }
    }
}