Iterator 提供一种方法顺序访问一个对象中各个元素，而又不需要暴露该对象的内部表示

Aggregate
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Test.Iterator
 6{
 7    public interface Aggregate
 8    {
 9        Iterator CreateIterator();
10    }
11}
12

ConcreteAggregate
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Test.Iterator
 6{
 7    public class ConcreteAggregate : Aggregate
 8    {
 9        Aggregate 成员#region Aggregate 成员
10
11        public Iterator CreateIterator()
12        {
13            return new ConcreteIterator(this);
14        }
15
16        #endregion
17
18        private System.Collections.ArrayList items = new System.Collections.ArrayList();
19
20        public int Count
21        {
22            get
23            {
24                return items.Count;
25            }
26        }
27
28        public object this[int index]
29        {
30            get
31            {
32                return (object)items[index];
33            }
34            set
35            {
36                items.Insert(index, value);
37            }
38        }
39    }
40}

Iterator
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Test.Iterator
 6{
 7    public interface Iterator
 8    {
 9        object First();
10        object Next();
11        bool isDone();
12        object Current();
13    }
14}

ConcreteIterator
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Test.Iterator
 6{
 7    public class ConcreteIterator : Iterator
 8    {
 9        private ConcreteAggregate concreteAggregate;
10        private int current = 0;
11
12        public ConcreteIterator(ConcreteAggregate t)
13        {
14            concreteAggregate = t;  
15        }
16
17        Iterator 成员#region Iterator 成员
18
19        public object First()
20        {
21            return concreteAggregate[0];
22        }
23
24        public object Next()
25        {
26            if (current < concreteAggregate.Count - 1)
27            {
28                return concreteAggregate[current++];
29            }
30            return null;
31        }
32
33        public bool isDone()
34        {
35            return current >= concreteAggregate.Count ? true : false;
36        }
37
38        public object Current()
39        {
40            return concreteAggregate[current];
41        }
42
43        #endregion
44    }
45}

客户代码
 1            ConcreteAggregate a = new ConcreteAggregate();
 2            a[0] = "0";
 3            a[1] = "00";
 4            a[2] = "000";
 5            a[3] = "0000";
 6            a[4] = "00000";
 7            a[5] = "000000";
 8
 9            ConcreteIterator i = new ConcreteIterator(a);
10
11            Console.WriteLine("begin");
12
13            object item = i.First();
14
15            while (item != null)
16            {
17                Console.WriteLine(item);
18                item = i.Next();
19            }
20
21            Console.ReadKey();