csc abstractshape.cs shapes.cs shapetest.cs
这样将生成可执行文件 shapetest.exe。
该文件声明的 Shape 类包含 double 类型的 Area 属性。
// compile with: csc /target:library abstractshape.cs
public abstract class Shape
{
private string name;
public Shape(string s)
{
// calling the set accessor of the Id property.
Id = s;
}
public string Id
{
get
{
return name;
}
set
{
name = value;
}
}
// Area is a read-only property - only a get accessor is needed:
public abstract double Area
{
get;
}
public override string ToString()
{
return Id + " Area = " + string.Format("{0:F2}", Area);
}
}
属性的修饰符就放置在属性声明中。例如：
public abstract double Area
声明抽象属性时（如本示例中的 Area），指明哪些属性访问器可用即可，不要实现它们。在此示例中，只有一个 get 访问器可用，因此该属性是只读的。
下面的代码演示 Shape 的三个子类，并演示它们如何重写 Area 属性来提供自己的实现。
// compile with: csc /target:library /reference:abstractshape.dll shapes.cs
public class Square : Shape
{
private int side;
public Square(int side, string id)
: base(id)
{
this.side = side;
}
public override double Area
{
get
{
// Given the side, return the area of a square:
return side * side;
}
}
}
public class Circle : Shape
{
private int radius;
public Circle(int radius, string id)
: base(id)
{
this.radius = radius;
}
public override double Area
{
get
{
// Given the radius, return the area of a circle:
return radius * radius * System.Math.PI;
}
}
}
public class Rectangle : Shape
{
private int width;
private int height;
public Rectangle(int width, int height, string id)
: base(id)
{
this.width = width;
this.height = height;
}
public override double Area
{
get
{
// Given the width and height, return the area of a rectangle:
return width * height;
}
}
}
下面的代码演示一个测试程序，它创建若干 Shape 派生对象，并输出它们的面积。
// compile with: csc /reference:abstractshape.dll;shapes.dll shapetest.cs
class TestClass
{
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);
}
}
}
