行为型设计模式之访问者模式

 1  using System;
 2 
 3     abstract class Visitor 
 4     {
 5         abstract public void VisitElementA(ConcreteElementA a);
 6         abstract public void VisitElementB(ConcreteElementB b);
 7     }
 8 
 9     class ConcreteVisitor1 : Visitor
10     {
11         override public void VisitElementA(ConcreteElementA a)
12         {
13             
14         }
15 
16         override public void VisitElementB(ConcreteElementB b)
17         {
18             
19         }
20     }
21 
22     abstract class Element 
23     {
24         abstract public void Accept(Visitor v);
25     }
26 
27     class ConcreteElementA : Element 
28     {
29         public Visitor myVisitor;
30         override public void Accept(Visitor v)
31         {
32             myVisitor = v;            
33         }
34 
35         public void OperationA()
36         {
37             
38         }
39 
40         public void DoSomeWork()
41         {
42             // do some work here
43             // . . .
44 
45             // Get visitor to visit
46             myVisitor.VisitElementA(this);        
47 
48             // do some more work here
49             // . . .
50         }
51     }
52 
53     class ConcreteElementB : Element 
54     {
55         override public void Accept(Visitor v)
56         {
57             
58         }
59 
60         public void OperationB()
61         {
62             
63         }
64     }
65 
66     /// <summary>
67     ///    Summary description for Client.
68     /// </summary>
69     public class Client
70     {
71         public static int Main(string[] args)
72         {            
73             ConcreteElementA eA = new ConcreteElementA();
74             ConcreteElementB eB = new ConcreteElementB();
75             ConcreteVisitor1 v1 = new ConcreteVisitor1();
76 
77             eA.Accept(v1);
78             eA.DoSomeWork();
79 
80             return 0;
81         }
82     }