copy of pointcircletest.cs

来自「this is a good book for the visual c#」· CS 代码 · 共 53 行

// Fig. 10.3: PointCircleTest.cs
// Demonstrating inheritance and polymorphism.

using System;
using System.Windows.Forms;

// PointCircleTest class definition
class PointCircleTest
{
   // main entry point for application.
   static void Main( string[] args )
   {
      Point point1 = new Point( 30, 50 );
      Circle circle1 = new Circle( 120, 89, 2.7 );

      string output = "Point point1: " + point1.ToString() +
         "\nCircle circle1: " + circle1.ToString();

      // use `is a' relationship to assign 
      // Circle circle1 to Point reference
      Point point2 = circle1;

      output += "\n\nCCircle circle1 (via point2): " + 
         point2.ToString();

      // downcast (cast base-class reference to derived-class
      // data type) point2 to Circle circle2
      Circle circle2 = ( Circle ) point2;

      output += "\n\nCircle circle1 (via circle2): " + 
         circle2.ToString();

      output += "\nArea of circle1 (via circle2): " + 
         circle2.Area();

      // attempt to assign point1 object to Circle reference
      if ( point1 is Circle )
      {
         circle2 = ( Circle ) point1;
         output += "\n\ncast successful";
      }
      else
      {
         output += "\n\npoint1 does not refer to a Circle";
      }

      MessageBox.Show( output, 
         "Demonstrating the `is a' relationship" );

   } // end method Main

} // end class PointCircleTest