求C#大神解释一下这道题 关于使用new关键字修饰.
public abstract class A{ public A() { Console.WriteLine('A'); } public virtual void Fun() { Console.WriteLine("A.Fun()"); }}public class B : A{ public B() { Console.WriteLine('B'); } public new void Fun() { Console.WriteLine("B.Fun()"); } public static void Main() { A a = new B(); a.Fun(); }}