C#类和属性的使用

C#类和属性的使用

abstractshape.cs

// abstractshape.cs
// 编译时使用：/target:library
// csc /target:library abstractshape.cs
using System;
public abstract class Shape
{
   private string myId;
   public Shape(string s)
   {
      Id = s;   // 调用 Id 属性的 set 访问器
   }
   public string Id
   {
      get 
      {
         return myId;
      }
      set
      {
         myId = value;
      }
   }
   // Area 为只读属性 - 只需要 get 访问器：
   public abstract double Area
   {
      get;
   }
   public override string ToString()
   {
      return Id + " Area = " + string.Format("{0:F2}",Area);
   }
}

shapes.cs

// shapes.cs
// 编译时使用：/target:library /reference:abstractshape.dll
public class Square : Shape
{
   private int mySide;
   public Square(int side, string id) : base(id)
   {
      mySide = side;
   }
   public override double Area
   {
      get
      {
         // 已知边长，返回正方形的面积：
         return mySide * mySide;
      }
   }
}
public class Circle : Shape
{
   private int myRadius;
   public Circle(int radius, string id) : base(id)
   {
      myRadius = radius;
   }
   public override double Area
   {
      get
      {
         // 已知半径，返回圆的面积：
         return myRadius * myRadius * System.Math.PI;
      }
   }
}
public class Rectangle : Shape
{
   private int myWidth;
   private int myHeight;
   public Rectangle(int width, int height, string id) : base(id)
   {
      myWidth  = width;
      myHeight = height;
   }
   public override double Area
   {
      get
      {
         // 已知宽度和高度，返回矩形的面积：
         return myWidth * myHeight;
      }
   }
}

shapetest.cs

// shapetest.cs
// 编译时使用：/reference:abstractshape.dll;shapes.dll
public class TestClass
{
   public static void Main()
   {
      Shape[] shapes =
         {
            new Square(5, "Square #1"),
            new Circle(3, "Circle #1"),
            new Rectangle( 4, 5, "Rectangle #1")
         };
      
      System.Console.WriteLine("Shapes Collection");
      foreach(Shape s in shapes)
      {
         System.Console.WriteLine(s);
      }
         
   }
}