1     public abstract class Element
 2     {
 3         public abstract void DoSomething();
 4         public void Accept(IVisitor visitor)
 5         {
 6             visitor.Visit(this);
 7         }
 8     }
 9     public class House : Element
10     {
11         public override void DoSomething()
12         {
13             //TODO show your house
14             Console.WriteLine("welcome to my house!");
15         }
16     }
17     public class Park : Element
18     {
19         public override void DoSomething()
20         {
21             //TODO enjoy yourself
22             Console.WriteLine("pick the ticket");
23         }
24     }
25     public interface IVisitor
26     {
27         void Visit(Element e);
28     }
29     public class Friend : IVisitor
30     {
31         public void Visit(Element e)
32         {
33             //To do。。
34             Console.WriteLine("i go to visit a friend");
35             e.DoSomething();
36 
37         }
38     }
39     public class ElementCollection
40     {
41         private IList<Element> elements = new List<Element>();
42         public IList<Element> Elements
43         {
44             get { return elements; }
45         }
46         public void AddElement(Element e)
47         {
48             Elements.Add(e);
49         }
50         public void RemoveElement(Element e)
51         {
52             Elements.Remove(e);
53         }
54     }
55     public class VisitorClient
56     {
57         public void Test()
58         {
59             Friend friend = new Friend();
60             ElementCollection elementCollection = new ElementCollection();
61             //初始化集合
62             for (int i = 0; i < 10; i++)
63             {
64                 if (i < 5)
65                 {
66                     elementCollection.AddElement(new House());
67                 }
68                 else
69                 {
70                     elementCollection.AddElement(new Park());
71                 }
72             }
73             //集合元素接受访问
74             foreach (var item in elementCollection.Elements)
75             {
76                 item.Accept(friend);
77             }
78         }
79     }