C# 跨线程交互

Question

有人可以帮助我如何在我的类中设置 Thread.join() 方法，或者是否有一种巧妙的方法来处理 SynchronizationContext 类和 thread.join 方法。基本上，我试图从不同的线程（不是 UI 线程）每 2 秒更新一次 datagridview (dgv) 单元格和进度条 (pb)。当一个线程完成这项工作时，该功能可以正常工作；但是，我想设置 2 个线程，以便第一个线程（线程 1）将更新控件（在我的例子中，它将更新 datagridview 并显示 10 行，进度条将更新到 50%）。一旦线程 1 完成其工作，线程 2 就应该启动并更新控件（在我的例子中，它将更新 datagridview 并显示另外 10 行，进度条将更新到 100%）。请参阅下面的代码。

using System;
using System.Diagnostics;
using System.Threading;
using System.Windows.Forms;

namespace DelegatesAndCallback
{
public partial class Form1 : Form
{
    private Thread newThread1;
    private Thread newThread2;

    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {

        int id = Thread.CurrentThread.ManagedThreadId;
        Trace.WriteLine("Button thread "+id);

        SynchronizationContext uiContext = SynchronizationContext.Current;

        // thread #1
        startThread1(uiContext);

        // thread #2
        startThread2(uiContext);
    }

    public void startThread1(SynchronizationContext sc)
    {
        // thread #1
        newThread1 = new Thread(Process1) { Name = "Thread 1" };
        newThread1.Start(sc);
        //newThread1.Join();
    }

    public void startThread2(SynchronizationContext sc)
    {
        // thread #2
        newThread2 = new Thread(Process2) { Name = "Thread 2" };
        newThread2.Start(sc);
        //newThread2.Join();
    }

    public  void updateProgressBarValue(object state)
    {
        double val = Convert.ToDouble(state)/19.0;
        pb.Value = (int)(100*val);
    }

    public  void updateDataGridViewValue(object state)
    {
        dgv.Rows.Add((int) state, (int) state);
    }

    public void Process1(object state)
    {
        SynchronizationContext uiContext = state as SynchronizationContext;

        for (int i = 0; i < 10; i++)
        {
            uiContext.Send(updateDataGridViewValue, i);
            uiContext.Send(updateProgressBarValue, i);
            Thread.Sleep(2000);
        }
    }

    public void Process2(object state)
    {
        SynchronizationContext uiContext = state as SynchronizationContext;

        for (int i = 10; i < 20; i++)
        {
            if (uiContext != null) uiContext.Send(updateProgressBarValue, i);
            if (uiContext != null) uiContext.Send(updateDataGridViewValue, i);
            Thread.Sleep(2000);
        }
    }
}
}

Answer 1

请参阅 Control.Invoke()，它专门设计用于让非UI 线程与进度条等交互。在这种情况下，使用 Invoke 将取代您的同步上下文以及对其 Send() 方法的使用。

稍微相关的说明：创建线程的更简单的方法是：

new Thread(
  () => {
   /// insert code you want executed in a separate thread here...
  }
  ).Start();

更新
如果您需要从不同的类更新进度条，我可能会这样做：

public partial class Form1 : Form
{
    private ThreadOwner _threadOwner;

    public Form1()
    {
        InitializeComponent();
        var _threadOwner = new ThreadOwner();
        _threadOwner.StartAThread(this,progressBar1.Minimum,progressBar1.Maximum);
    }

    protected override void OnClosing(CancelEventArgs e)
    {
        _threadOwner.Exit();

        base.OnClosing(e);
    }

    internal void SetProgress(int progress)
    {
        if (progressBar1.InvokeRequired)
        {
            progressBar1.Invoke(
                new Action<Form1>(
                    (sender) => { 
                        SetProgress(progress); 
                    }
                    ),new[] { this }
                    );

        }
        else
            progressBar1.Value = progress;
    }
}

ThreadOwner 类：

public class ThreadOwner
{
    private bool _done = false;

    public void StartAThread(Form1 form, int min, int max)
    {
        var progress = min;

        new Thread(() =>
            {
                while (!_done)
                {
                    form.SetProgress(progress);

                    if (progress++ > max)
                    {
                        progress = min;
                    }
                }

            }
        ).Start();
    }

    internal void Exit()
    {
        _done = true;
    }
}

要点是线程需要对表单实例的引用，该实例公开一个更新进度条的方法。然后该方法确保更新发生在正确的线程中。

Answer 2

要同步线程，您应该使用[Manual|Auto]ResetEvents。
您应该使用其他模式来编写安全的代码。
请调查我的代码：

public interface IProgress
{
    ManualResetEvent syncEvent { get; }
    void updateProgressBarValue(int state);
    void updateDataGridViewValue(int state);
}

public partial class Form1 : Form, IProgress
{
    // Sync object will be used to syncronize threads
    public ManualResetEvent syncEvent { get; private set; }

    public Form1()
    {
    }

    private void button1_Click(object sender, EventArgs e)
    {
        // Creeate sync object in unsignalled state
        syncEvent = new ManualResetEvent(false);

        // I like Async model to start background workers
        // That code will utilize threads from the thread pool
        ((Action<IProgress>)Process1).BeginInvoke(this, null, null);
        ((Action<IProgress>)Process2).BeginInvoke(this, null, null);
    }

    public void updateProgressBarValue(int state)
    {
        // InvokeRequired? -> Invoke pattern will prevent UI update from the non UI thread
        if (InvokeRequired)
        {
            // If current thread isn't UI method will invoke into UI thread itself
            Invoke((Action<int>)updateProgressBarValue, state);
            return;
        }

        double val = Convert.ToDouble(state) / 19.0;
        pb.Value = (int)(100 * val);
    }

    public void updateDataGridViewValue(int state)
    {
        if (InvokeRequired)
        {
            Invoke((Action<int>)updateDataGridViewValue, state);
            return;
        }

        dgv.Rows.Add((int)state, (int)state);
    }

    public void Process1(IProgress progress)
    {
        for (int i = 0; i < 10; i++)
        {
            // We have InvokeRequired in the methods and don't need any other code to invoke it in UI thread
            progress.updateDataGridViewValue(i);
            progress.updateProgressBarValue(i);
            Thread.Sleep(2000);
        }

        // When thread 1 complete its job we will set sync object to signalled state to wake up thread 2
        syncEvent.Set();
    }

    public void Process2(IProgress progress)
    {
        // Thread 2 will stop until sync object signalled
        syncEvent.WaitOne();

        for (int i = 10; i < 20; i++)
        {
            progress.updateProgressBarValue(i);
            progress.updateDataGridViewValue(i);
            Thread.Sleep(2000);
        }
    }
}

代码已更新以从不同的类调用 UI 更新