如何保护来自另一个线程的数据以在控件上使用？

Question

我有一个库，它使用来自异步 tcp 操作的事件数据提供服务。 当在 UI 上收到这些数据后在控件中使用这些数据时，我收到了跨线程操作异常。如何在图书馆的使用者获得要在其控件上显示的数据之前解决此问题。所以基本上我需要将数据扔到他自己的线程中使用该库？

与带有链接文件的紧凑框架使用的代码相同。

我在库内部使用此方法和帮助控件来说明是否需要调用但它不起作用。

public static void InvokeIfNecessary(Control control, Action setValue)
{

    if (control.InvokeRequired)
    {
        control.Invoke(setValue);
    }
    else
    {
        setValue();
    }
}

使用事件向使用该库的用户提供数据的示例代码。

    if (OnClientChangeConnection != null) SafeData.InvokeIfNecessary(_helpControl, () => OnClientChangeConnection(ConnectedClients, requestClientInfo)); // ConnectedClients is an integer and requestClientInfo is a List<ClientInfo> class type.

谢谢。

Answer 1

执行此操作的正确方法是使用 SynchronizationContext 对象。我已经包含了示例代码。基本上，您要做的就是将线程任务包装在一个类中，该类可以保存对主线程提供的同步上下文对象和回调的引用，然后在工作结束后调用这些对象。

这是一个简单的形式：

public partial class Form1 : Form
{
    private SynchronizationContext _synchronizationContext;

    public Form1()
    {
        InitializeComponent();
        //Client must be careful to create sync context soimehwere they are sure to be on main thread
        _synchronizationContext = AsyncOperationManager.SynchronizationContext;
    }

    //Callback method implementation - must be of this form
    public void ReceiveThreadData(object threadData)
    {
        // Can use directly in UI without error
        this.listBoxMain.Items.Add((string)threadData);
    }

    private void DoSomeThreadWork()
    {
        // Thread needs callback and sync context.  
        // You probably want to derive your own callback from the NET SendOrPostCallback class.
        SendOrPostCallback callback = new SendOrPostCallback(ReceiveThreadData);
        SomeThreadTask task = new SomeThreadTask(_synchronizationContext, callback);
        Thread thread = new Thread(task.ExecuteThreadTask);
        thread.Start();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        DoSomeThreadWork();
    }

}

这是一个具有线程任务的类

/// SomeThreadTask defines the work a thread needs to do and also provides any data required along with callback pointers etc.
/// Populate a new SomeThreadTask instance with a synch context and callnbackl along with any data the thread needs
/// then start the thread to execute the task.
/// </summary>
public class SomeThreadTask
{

    private string _taskId;
    private SendOrPostCallback _completedCallback;
    private SynchronizationContext _synchronizationContext;

    /// <summary>
    /// Get instance of a delegate used to notify the main thread when done.
    /// </summary>
    internal SendOrPostCallback CompletedCallback
    {
        get { return _completedCallback; }
    }

    /// <summary>
    /// Get SynchronizationContext for main thread.
    /// </summary>
    internal SynchronizationContext SynchronizationContext
    {
        get { return _synchronizationContext; }
    }

    /// <summary>
    /// Thread entry point function.
    /// </summary>
    public void ExecuteThreadTask()
    {

        //Just sleep instead of doing any real work
        Thread.Sleep(5000);

        string message = "This is some spoof data from thread work.";

        // Execute callback on synch context to tell main thread this task is done.
        SynchronizationContext.Post(CompletedCallback, (object)message);


    }

    public SomeThreadTask(SynchronizationContext synchronizationContext, SendOrPostCallback callback)
    {
        _synchronizationContext = synchronizationContext;
        _completedCallback = callback;
    }

}

Answer 2

您可以从 UI 线程保存对 SynchronizationContext.Current 的引用，然后调用其 Post 或 Send 方法在 UI 线程上运行代码。