两个线程的同步

Question

我在c#中有两个线程.现在我需要等待一个特定的语句执行才能继续执行另一个线程,这显然是同步的情况.是否有任何代码可以像使用内置方法一样执行此操作？

这是代码示例:

    public void StartAccept()
    {
            try
            {
                newSock.BeginAccept(new AsyncCallback(Accepted), newSock);
            }
            catch (ArgumentException)
            {
                MessageBox.Show("Error in arguments while using begin-accept", "Error", MessageBoxButtons.OK);
            }
            catch (ObjectDisposedException)
            {
                MessageBox.Show("socket closed while using begin-accept", "Error", MessageBoxButtons.OK);
            }
            catch (SocketException)
            {
                MessageBox.Show("Error accessing socket while using begin-accept", "Error", MessageBoxButtons.OK);
            }
            catch (InvalidOperationException)
            {
                MessageBox.Show("Invalid operation while using begin-accept", "Error", MessageBoxButtons.OK);
            }
            catch (Exception)
            {
                MessageBox.Show("Exception occurred while using begin-accept", "Error", MessageBoxButtons.OK);
            }

    }

这将从代码选择的所需主机接收数据:

    private void listBox1_Click(object sender, EventArgs e)
    {



        String data = (String)this.listBox1.SelectedItem;

        ip = Dns.GetHostAddresses(data);

        clientIP = new IPEndPoint(ip[0], 5555);

        newSock.Bind(clientIP);
        newSock.Listen(100);

    }

因此,为了开始接收数据,我需要将套接字初始化为特定的远程主机,这是在我单击列表框中显示的其中一个主机时完成的.为此,我需要同步.

Answer 1

看一下AutoResetEvent和ManualResetEvent.它们是使线程之间的同步成为可能的信号.

需要等待完成某事的第一个线程将执行myEvent.WaitOne(),阻塞直到另一个线程调用myEvent.设置().

假设我们有两个线程,其中一个线程需要在另一个线程可以继续之前进行某种初始化.然后在两者之间共享一个AutoResetEvent,让我们称之为myEvent.

// Signal example

using System;
using System.Threading;

class MySync
{
    private readonly AutoResetEvent _myEvent;
    public MySync(AutoResetEvent myEvent)
    {
        _myEvent = myEvent;
    }

    public void ThreadMain(object state)
    {
        Console.WriteLine("Starting thread MySync");
        _myEvent.WaitOne();
        Console.WriteLine("Finishing thread MySync");
    }
}

class Program
{
    static void Main(string[] args)
    {
        AutoResetEvent myEvent = new AutoResetEvent(false);
        MySync mySync = new MySync(myEvent);
        ThreadPool.QueueUserWorkItem(mySync.ThreadMain);
        Console.WriteLine("Press enter to continue...");
        Console.ReadLine();
        myEvent.Set();
        Console.WriteLine("Press enter to continue...");
        Console.ReadLine();
        Console.WriteLine("Finishing");
    }
}

不要将此与访问顺序无关紧要的共享资源混淆.例如,如果您有共享列表或共享字典,则需要将其包装在互斥锁中以确保它们正确执行.

// Mutex example

object mySync = new object();
Dictionary<int, int> myDict = new Dictionary<int, int>();

void threadMainA()
{
    lock(mySync)
    {
        mySync[foo] = bar;
    }
}

void threadMainB()
{
    lock(mySync)
    {
        mySync[bar] = foo;
    }
}