［多线程问题］这个多线程该怎么写？

Question

  做了一个WinForm程序，自动检测是否插入了U盘等移动存储设备，若插入了就把硬盘文件下的文件复制到U盘上去，当插入多个U盘时，同时往多个U盘中写数据。现在只实现了往一个U盘上写数据，等待当前的U盘写完数据后再往下一个U盘中写数据，要同是往多个U盘中同时写数据，用多线程该怎么写？

Answer 1

to  windily 
-----------------------------
我做的winForm是往多张mini SD卡上写复制数据，把硬盘上的某个文件夹下的文件复制到多个mini SD卡中，现在我只要换卡和取卡就可以了。。顺便公布一下写的多线程代码：
 #region Class  MyThread
    class MyThread
    {
        public static Dictionary<string, bool> status = new Dictionary<string, bool>();
        public static void CopyDirectory(object argu)
        {
            string Src = (argu as ThreadMethodHelper).Src;
            string Dst = (argu as ThreadMethodHelper).Dst;            if (status.ContainsKey(Dst))
                status[Dst] = false;
            else
                status.Add(Dst, false);            String[] Files;
            if (Dst[Dst.Length - 1] != Path.DirectorySeparatorChar)
                Dst += Path.DirectorySeparatorChar;            if (!Directory.Exists(Dst))
                Directory.CreateDirectory(Dst);            Files = Directory.GetFileSystemEntries(Src);
           
            foreach (string Element in Files)
            {
                // Sub directories
                if (Directory.Exists(Element))
                {
                    //copyDirectory(Element, Dst + Path.GetFileName(Element));
                    ThreadMethodHelper args = new ThreadMethodHelper();
                    args.Src = Element;
                    args.Dst = Dst + Path.GetFileName(Element);
                    Thread my = new Thread(new ParameterizedThreadStart(CopyDirectory));
                    my.Start(args);
                    my.Join();                    
                }
                // Files in directory
                else
                {                    
                    File.Copy(Element, Dst + Path.GetFileName(Element), true);
                }
            }
            status[Dst] = true;
        }
    }
    #endregion    class ThreadMethodHelper
    {
        public string Src;
        public string Dst;
      
    }

Answer 2

to  windily 
-----------------------------
我做的winForm是往多张mini SD卡上写复制数据，把硬盘上的某个文件夹下的文件复制到多个mini SD卡中，现在我只要换卡和取卡就可以了。。顺便公布一下写的多线程代码：
 #region Class  MyThread
    class MyThread
    {
        public static Dictionary<string, bool> status = new Dictionary<string, bool>();
        public static void CopyDirectory(object argu)
        {
            string Src = (argu as ThreadMethodHelper).Src;
            string Dst = (argu as ThreadMethodHelper).Dst;            if (status.ContainsKey(Dst))
                status[Dst] = false;
            else
                status.Add(Dst, false);            String[] Files;
            if (Dst[Dst.Length - 1] != Path.DirectorySeparatorChar)
                Dst += Path.DirectorySeparatorChar;            if (!Directory.Exists(Dst))
                Directory.CreateDirectory(Dst);            Files = Directory.GetFileSystemEntries(Src);
           
            foreach (string Element in Files)
            {
                // Sub directories
                if (Directory.Exists(Element))
                {
                    //copyDirectory(Element, Dst + Path.GetFileName(Element));
                    ThreadMethodHelper args = new ThreadMethodHelper();
                    args.Src = Element;
                    args.Dst = Dst + Path.GetFileName(Element);
                    Thread my = new Thread(new ParameterizedThreadStart(CopyDirectory));
                    my.Start(args);
                    my.Join();                    
                }
                // Files in directory
                else
                {                    
                    File.Copy(Element, Dst + Path.GetFileName(Element), true);
                }
            }
            status[Dst] = true;
        }
    }
    #endregion    class ThreadMethodHelper
    {
        public string Src;
        public string Dst;
      
    }

Answer 3

        #region CheckDisk
        private void CheckDisk()
        { 
            char Char = this.textBox2.Text.Substring(0, 1).ToCharArray()[0];
            int Int = (int)Char;            
            for (int i = 0; i < 5; i++)
            {
                char thePath = (char)(Int + i);
                string path = thePath.ToString() + @":\";
                if (Directory.Exists(path))
                {                   
                    if (MyThread.status.ContainsKey(path))
                    {
                        if (MyThread.status[path])      //判断是否己拷贝文件
                        {
                            Exsits += path + "己准备\n";
                            result+= path + "己拷贝完成\n";
                        }
                        else
                        {
                            Exsits += path + "己准备\n";
                            ThreadMethodHelper argu = new ThreadMethodHelper();
                            result += path + "正在拷贝文件.....\n";
                            argu.Src = this.textBox1.Text;
                            argu.Dst = path;
                            Thread t = new Thread(new ParameterizedThreadStart(MyThread.CopyDirectory));
                            t.Start(argu);                                                      
                        }
                    }
                    else
                    {
                        //拷贝文件  
                        Exsits += path+"己准备\n";
                        ThreadMethodHelper argu = new ThreadMethodHelper();
                        result += path + "正在拷贝文件.....\n";
                        argu.Src = this.textBox1.Text;
                        argu.Dst = path;
                        Thread t = new Thread(new ParameterizedThreadStart(MyThread.CopyDirectory));
                        t.Start(argu);                                        
                    }
                }
                else
                {
                    Exsits += path+"不存在\n";     //不存在盘符
                    MyThread.status.Remove(path);
                }
            }
        }
        #endregion        #region timer1_Tick
        private void timer1_Tick(object sender, EventArgs e)
         {
            
            Exsits = string.Empty;
            result = string.Empty;
            Thread th = new Thread(CheckDisk);
            th.Start();
            th.Join();
            this.richTextBox1.Text = Exsits;
            this.richTextBox1.Refresh();
            this.richTextBox2.Text = result;
            this.richTextBox2.Refresh();
        }
        #endregion

Answer 4

我觉得你在CopyDirectory里面没必要再加线程了吧？
my.Join(); 线程一直等待着，也没有提高性能啊，
在 for   (int   i   =   0;   i   <   5;   i++) 
个人认为循环里面加线程就可以了

Answer 5

刚测试了一下,的确如LZ所说的,多线程比单线程快.
我的见解是,不对的请指出:因为多个线程抢占cpu时间片概率比一个线程抢占cpu时间片的概率大,所以分的是使用时间多一点.但是如果系统只有你这个程序,没有其他程序在执行(包括windows的进程),那肯定是单线程快.
使用线程主要是因为它可以同时对不同的资源进行访问,而不是因为它同时对一个资源进行访问.