C# 子类父类方法同名，三种处理方式?

 1 using System;
 2 class A 
 3 {
 4     //虚方法
 5     virtual public void sayHello(){
 6         Console.WriteLine("A sayHello");
 7     }
 8 }
 9 class Test:A
10 {
11     override public void sayHello(){
12         base.sayHello();//访问父类的成员，使用关键词base
13         Console.WriteLine("Test sayHello");
14     }
15     static void Main( string [] args )
16     {
17         Test t = new Test();
18         t.sayHello();
19         Console.ReadLine();
20     }
21 }

 1 using System;
 2 abstract class A //含有抽象方法的类，抽象类
 3 {
 4     //抽象方法
 5     abstract public void sayHello();
 6 }
 7 class Test:A
 8 {
 9     override public void sayHello(){
10         Console.WriteLine("Test sayHello");
11     }
12     static void Main( string [] args )
13     {
14         Test t = new Test();
15         t.sayHello();
16         Console.ReadLine();
17     }
18 }