一句话：你是否真的了解new, override, virtual
下面代码的结果，如果基类使用接口代替，也是一样的效果。
主要注意看override或new了基类的方法后，调用方将子类对象转型为父类后的输出会有什么不同；
代码
class Program
{
static void Main( string [] args)
{
TestShape();
Console.WriteLine( " TestShape end ============= " + Environment.NewLine);
TestDerive();
Console.WriteLine( " TestDerive end ============= " + Environment.NewLine);
TestDerive2();
Console.WriteLine( " TestDerive2 end ============= " + Environment.NewLine);
Console.ReadKey();
}
private static void TestShape()
{
System.Collections.Generic.List < Shape > shapes = new System.Collections.Generic.List < Shape > ();
shapes.Add( new Circle());
shapes.Add( new Rectangle());
shapes.Add( new Triangle());
shapes.Add( new Diamond());
foreach (Shape s in shapes)
{
s.MethodVirtual();
s.Method();
Console.WriteLine();
}
}
private static void TestDerive()
{
Circle circle = new Circle();
Rectangle rectangle = new Rectangle();
Triangle triangel = new Triangle();
Diamond diamond = new Diamond();
circle.MethodVirtual();
circle.Method();
Console.WriteLine();
rectangle.MethodVirtual();
rectangle.Method();
Console.WriteLine();
triangel.MethodVirtual();
triangel.Method();
Console.WriteLine();
diamond.MethodVirtual();
diamond.Method();
Console.WriteLine();
}
private static void TestDerive2()
{
Circle circle = new Circle();
PrintShape(circle);
Rectangle rectangle = new Rectangle();
PrintShape(rectangle);
Triangle triangel = new Triangle();
PrintShape(triangel);
Diamond diamond = new Diamond();
PrintShape(diamond);
/// out put:
// circle override MethodVirtual
// base Method call
// base MethodVirtual call
// base Method call
// base MethodVirtual call
// base Method call
// base MethodVirtual call
// base Method call
}
static void PrintShape(Shape sharpe)
{
sharpe.MethodVirtual();
sharpe.Method();
Console.WriteLine();
}
}
public class Shape
{
public virtual void MethodVirtual()
{
Console.WriteLine( " base MethodVirtual call " );
}
public void Method()
{
Console.WriteLine( " base Method call " );
}
}
/// 类描述：override了基类的virtual方法
///
/// 第一种使用方法：转型为父类
/// sharp s = new Circle()
/// s.MethodVirtual();
/// s.Method();
/// 因为子类已经override了父类的MethodVirtual，所以即使子类转型为了sharp，调用的还是子类的方法
/// out put:
/// circle override MethodVirtual
/// base Method call
///
/// 第二类使用方法：使用子类本身
/// 这很好理解，全部输出的是子类的方法
/// Circle circle = new Circle();
/// circle.MethodVirtual();
/// circle.Method();
/// out put:
/// circle override MethodVirtual
/// base Method call
class Circle : Shape
{
public override void MethodVirtual()
{
Console.WriteLine( " circle override MethodVirtual " );
}
}
/// 类描述：未做任何处理
///
/// 第一种使用方法
/// sharp s = new Rectangle()
/// s.MethodVirtual();
/// s.Method();
/// out put:
/// base MethodVirtual call
/// base Method call
///
/// 第二类使用方法：使用子类本身
/// 这很好理解，全部输出的是子类的方法
/// Rectangle rectangle = new Rectangle();
/// rectangle.MethodVirtual();
/// rectangle.Method();
/// out put:
/// base MethodVirtual call
/// base Method call
class Rectangle : Shape
{
}
/// 类描述：new了基类的虚方法即非虚方法
///
/// 第一种使用方法
/// sharp s = new Triangle()
/// s.MethodVirtual();
/// s.Method();
/// 因为子类已经new了父类的方法，所以s输出的是父类的方法
/// out put:
/// base MethodVirtual call
/// base Method call
///
/// 第二类使用方法：使用子类本身
/// 这很好理解，全部输出的是子类的方法
/// Triangle triangel = new Triangle();
/// triangel.MethodVirtual();
/// triangel.Method();
/// out put:
/// triangle new MethodVirtual
/// triangle new Method
class Triangle : Shape
{
public new void MethodVirtual()
{
Console.WriteLine( " triangle new MethodVirtual " );
}
public new void Method()
{
Console.WriteLine( " triangle new Method " );
}
}
/// 类描述：创建了基类方法相同的方法，未new及override
/// 编译器会做提示“隐藏继承”，并有如存在 new 关键字一样执行操作
///
/// 第一种使用方法
/// sharp s = new Diamond()
/// s.MethodVirtual();
/// s.Method();
/// 因为默认new的效果，所以输出和显式new修饰的一样
/// out put:
/// base MethodVirtual call
/// base Method call
///
/// 第二类使用方法：使用子类本身
/// 这很好理解，全部输出的是子类的方法
/// Diamond diamond = new Diamond();
/// diamond.MethodVirtual();
/// diamond.Method();
/// out put:
/// Diamond default MethodVirtual
/// Diamond default Method
class Diamond : Shape
{
public void MethodVirtual()
{
Console.WriteLine( " Diamond default MethodVirtual " );
}
public void Method()
{
Console.WriteLine( " Diamond default Method " );
}
}
本文转自最课程陆敏技博客园博客，原文链接：http://www.cnblogs.com/luminji/archive/2011/02/08/1950001.html，如需转载请自行联系原作者
