Command 在一个对象中封装一个请求

菜单命令

ShowCommand
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4using System.Windows.Forms;
 5
 6namespace Gof.Test.Command
 7{
 8    public class ShowCommand : System.Windows.Forms.Form
 9    {
10        public ShowCommand()
11        {
12            MenuItem exitItem = new MenuItem();
13            exitItem.Text = "退出";
14            exitItem.Click += new EventHandler(Excite);
15             
16            Menu = new MainMenu();
17            Menu.MenuItems.Add(exitItem);
18        }
19        public void Excite(object o, EventArgs e)
20        {
21            Console.WriteLine("Exit");
22        }
23    }
24}

客户代码
1System.Windows.Forms.Application.Run(new ShowCommand());
2

利用命令模式提供一个服务

DataService
  1using System;
  2using System.Collections.Generic;
  3using System.Text;
  4using System.Data;
  5using System.Data.OleDb;
  6using System.Reflection;
  7using System.IO;
  8
  9namespace Gof.Test.Command
 10{
 11    public delegate object BorrowReader(IDataReader reader);
 12    public class DataService
 13    {
 14        public DataService()
 15        { }
 16
 17        public static DataTable CreateTable(string select)
 18        {
 19            return (DataTable) GetDataReader(select,new BorrowReader(CreateTable));
 20        }
 21
 22        internal static DataTable CreateTable(IDataReader reader)
 23        {
 24            DataTable table = new DataTable();
 25            for (int i = 0; i < reader.FieldCount; i++)
 26            {
 27                table.Columns.Add(reader.GetName(i), reader.GetFieldType(i));
 28            }
 29
 30            while (reader.Read())
 31            {
 32                DataRow dr = table.NewRow();
 33                for (int i = 0; i < reader.FieldCount; i++)
 34                {
 35                    dr[i] = reader.GetValue(i);
 36                }
 37                table.Rows.Add(dr);
 38            }
 39            return table;
 40        }
 41
 42        public static object GetDataReader(string sel, BorrowReader borrow)
 43        {
 44            try
 45            {
 46                using (OleDbConnection con = CreateConnection())
 47                {
 48                    con.Open();
 49                    OleDbCommand com = new OleDbCommand();
 50                    com.Connection = con;
 51                    com.CommandText = sel;
 52                    OleDbDataReader reader = com.ExecuteReader();
 53                    return borrow(reader);
 54                }
 55            }
 56            catch (Exception ex)
 57            {
 58                throw ex;//不处理了
 59            }
 60        }
 61
 62        public static OleDbConnection CreateConnection()
 63        {
 64            string fileName = GetFileName("db", "oozinoz.mdb");
 65            OleDbConnection con = new OleDbConnection();
 66            con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + fileName;
 67            return con;
 68        }
 69
 70        public static String GetFileName(String dirName, String fileName)
 71        {
 72            String path;
 73            // Can we find the file using the OOZINOZ environment variable?
 74            String oozinozBase = Environment.GetEnvironmentVariable("OOZINOZ");
 75            if (oozinozBase != null)
 76            {
 77                path = Path.Combine(Path.Combine(oozinozBase, dirName), fileName);
 78                if (File.Exists(path))
 79                {
 80                    return path;
 81                }
 82            }
 83            // How 'bout relative to where the bin files are?
 84            Assembly a = Assembly.GetAssembly(typeof(DataService));
 85            DirectoryInfo thisDir = Directory.GetParent(a.Location);
 86            DirectoryInfo parentDir = Directory.GetParent(thisDir.FullName);
 87            path = Path.Combine(
 88                parentDir.FullName,
 89                dirName + Path.DirectorySeparatorChar + fileName);
 90            if (File.Exists(path))
 91            {
 92                return path;
 93            }
 94            // Ok, how 'bout in the top-level directory?
 95            path = Path.Combine(Path.Combine(@"\ConsoleApplication2", dirName), fileName);
 96            if (File.Exists(path))
 97            {
 98                return path;
 99            }
100            // dang
101            throw new Exception("FileFinder.GetFileName() cannot find " + fileName + " in directory " + dirName);
102
103        }
104    }
105}

命令模式的钩子

命令模式钩子
 1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4
 5namespace Gof.Test.Command
 6{
 7   public delegate void BeforDoSomething();
 8
 9    public class DelegateForHook
10    {
11        public event BeforDoSomething befordosomething;
12
13        public void Begin()
14        {
15            Console.WriteLine("Begin");
16        }
17
18        public void DoSomething()
19        {
20            Console.WriteLine("Do Something");
21        }
22
23        public void End()
24        {
25            Console.WriteLine("End");
26        }
27
28        public void DoWork()
29        {
30            Begin();
31            if (befordosomething != null)
32            {
33                befordosomething();
34            }
35            DoSomething();
36            End();
37        }
38    }
39}

客户代码
1      DelegateForHook delegateforhook = new DelegateForHook();
2            delegateforhook.befordosomething += new BeforDoSomething(MyBeforDoSomethingMethod);
3            delegateforhook.DoWork();
4            Console.ReadKey();

The Command Pattern encapsulates a request as an object, thereby letting you parameterize other objects with different requests, queue or log requests, and suppoert undoable operations.