c# - 关于继承

Question

为什么这段代码会产生输出“Base class”而不是“Derived2 class”？

namespace TestConsoleApplication
{ 
    class Baseclass
    { 
        public void fun()
        { 
            Console.Write("Base class" + " ");
        } 
    } 
    class Derived1: Baseclass
    { 
        new void fun()
        {
            Console.Write("Derived1 class" + " "); 
        } 
    } 
    class Derived2: Derived1
    { 
        new void fun()
        { 
            Console.Write("Derived2 class" + " ");
        }
    }
    class Program
    { 
        public static void Main(string[ ] args)
        { 
            Derived2 d = new Derived2(); 
            d.fun(); 
        } 
    } 
}

Answer 1

因为您没有将该方法声明为公共(public)的。

您已经告诉它隐藏原始定义，而不是覆盖它 - 它会做，但默认访问修饰符是private，不是公开的。

例如，当从 Derived2 中调用方法时:

class Derived2 : Derived1
{
    new void fun()
    {
        Console.Write("Derived2 class" + " ");
    }

    public void Test()
    {
        fun();
    }
}
class Program
{
    public static void Main(string[] args)
    {
        Derived2 d = new Derived2();
        d.Test(); //Prints 'Derived2 class'
    }
}

将其设置为 public 确实会在您的原始示例中打印 Derived2

public new void fun()
{
    Console.Write("Derived2 class" + " ");
}