C#-new 和 override 的区别

//override
public class A
...{
    public A()
    ...{
        Console.WriteLine("A constructing");       
        this.GetYear();
    }
    public virtual void GetYear()
    ...{
        Console.WriteLine("A");
    }
}
public class B:A
...{
    public B():base()
    ...{
        Console.WriteLine("B constructing");
        this.GetYear();
    }
    public override void GetYear()
    ...{
        Console.WriteLine("B");
    }
}
public class C : B
...{
    public C()
    ...{
        Console.WriteLine("C constructing");
        this.GetYear();
    }
    public override void GetYear()
    ...{
        Console.WriteLine("C");
    }
}
public class MyClass
...{
    public static void Main()
    ...{        
        C c = new C();
        Console.ReadLine();
    }    
}
/**//***************************************************
output:
    A constructing
    C
    B constructing
    C
    C constructing
    C
***************************************************/

//new
public class A
...{
    public A()
    ...{
        Console.WriteLine("A constructing");
        this.GetYear();
    }
    protected  void GetYear()
    ...{
        Console.WriteLine("A");
    }
}

public class B:A
...{
    public B()
    ...{
        Console.WriteLine("B constructing");
        this.GetYear();
    }
    protected void GetYear() //new写不写一样,但不写编译时会给警告
    ...{
        Console.WriteLine("B");
    }
}
public class C : B
...{
    public C()
    ...{
        Console.WriteLine("C constructing");
        this.GetYear();
    }

    protected new void  GetYear()
    ...{
        Console.WriteLine("C");
    }
}
public class MyClass
...{
    public static void Main()
    ...{        
        C c = new C();
        Console.ReadLine();
    }    
}
/**//***************************************************
output:
    A constructing
    A
    B constructing
    B
    C constructing
    C
***************************************************/

2007-09-08添加
override相当于C++中的重载,需要与virtual关键字配合使用;
new,说实话,不写也无妨,只是编译器会报警告,而它通常出现在子类与父类同名的函数中.

2007-11-3添加
        在第一个例子中,我开始错误的认为,如果此方法被子类重载了,无论是类A的实例还是类B的实例,调用此方法时,一律显示"C",其实不是这样的.应该是哪个类的实例去调用,就显示那个类中该方法的内容.
        而为什么我会错误的分析第一例,还是"this.GetYear();"这句闹的.

public class MyClass
...{
    class Father
    ...{
        public virtual void ShowMe()
        ...{
            Console.WriteLine("I am father.");
        }
        public void Talk()
        ...{
            Console.WriteLine("Father said...");
        }
    }
    class Child : Father
    ...{
        public override void ShowMe()
        ...{
            Console.WriteLine("I am child.");
        }
        public new void Talk()
        ...{
            Console.WriteLine("Child said...");
        }
    }
    public static void Main()
    ...{        
        Father fa = new Father();
        fa.ShowMe();//output : "I am father"
        fa.Talk();//output : "Father said..."
        Child ch = new Child();
        ch.ShowMe();//output : "I am child"
        ch.Talk();//output : "Child said..."
        Father fa1 = new Child();
        fa1.Talk();//output : "Father said..."
        fa1.ShowMe();//output : "I am child"
        RL();
    }