1using System;
2using System.Collections.Generic;
3using System.Text;
4using System.Data;
5
6namespace CompositeStudy
7{
8    /**//// <summary>
 9    /// 工厂类
10    /// </summary>
11    /// <remarks>工厂类</remarks>
12    public class ThreadFactory
13    {
14        DataTable table = new DataTable();
15        public ThreadFactory()
16        {
17            table.Columns.Add("content");
18            table.Columns.Add("IsTop");
19            table.Columns.Add("IsMessage");
20            table.Columns.Add("ID");
21            table.Columns.Add("ParentID");
22
23            DataRow row = table.NewRow();
24            row["content"] = "test";
25            row["IsTop"] = false;
26            row["IsMessage"] = false;
27            row["ID"] = 1;
28            row["ParentID"] = 0;
29            table.Rows.Add(row);
30
31            row = table.NewRow();
32            row["content"] = "test1";
33            row["IsTop"] = true;
34            row["IsMessage"] = false;
35            row["ID"] = 0;
36            row["ParentID"] = -1;
37            table.Rows.Add(row);
38
39            row = table.NewRow();
40            row["content"] = "test2";
41            row["IsTop"] = false;
42            row["IsMessage"] = true;
43            row["ID"] = 2;
44            row["ParentID"] = 0;
45            table.Rows.Add(row);
46
47            row = table.NewRow();
48            row["content"] = "test3";
49            row["IsTop"] = false;
50            row["IsMessage"] = true;
51            row["ID"] = 3;
52            row["ParentID"] = 0;
53            table.Rows.Add(row);
54        }
55        public List<IThread> GetTopThreads()
56        {
57            List<IThread> list = new List<IThread>();
58            DataRow[] rows = table.Select("IsTop = true");
59            foreach (DataRow row in rows)
60            {
61                Thread t = new Thread();
62                t.Content = row["content"].ToString();
63                t.IsTop = true;
64                DataRow[] cs = table.Select("ParentID="+Convert.ToInt32(row["ID"]));
65                foreach (DataRow r in cs)
66                {
67                    if (Convert.ToBoolean(r["IsMessage"]))
68                    {
69                        Message m = new Message();
70                        m.Content = r["content"].ToString();
71                        m.IsTop = false;
72                        t.Add(m);
73                    }
74                    else
75                    {
76                        Thread tt = new Thread();
77                        tt.Content = r["content"].ToString();
78                        tt.IsTop = false;
79                        t.Add(tt);
80                    }
81                }
82                list.Add(t);
83            }
84            return list;
85        }
86    }
87}

1using System;
2using System.Collections.Generic;
3using System.Text;
4
5namespace CompositeStudy
6{
7    class Program
8    {
9        static void Main(string[] args)
10        {
11            ThreadFactory factory = new ThreadFactory();
12            List<IThread> threads = factory.GetTopThreads();
13            foreach(IThread t in threads)
14            {
15                t.RenderContent();
16            }
17            Console.Read();
18        }
19    }
20}
21

1)         使客户端调用简单，客户端可以一致的使用组合结构或其中单个对象，用户就不必关心自己处理的是单个对象还是整个组合结构，这就简化了客户端代码。

2)       更容易在组合体内加入对象部件. 客户端不必因为加入了新的对象部件而更改代码。这一点符合开闭原则的要求，对系统的二次开发和功能扩展很有利！