好奇Control.Invoke的执行（） [英] Curious about the implementation of Control.Invoke()

问题描述

这到底是什么Control.Invoke（代表）做的就是委托给GUI线程上运行？此外，它的我的理解是调用将阻塞，直到被调用的函数将其完成。它是如何做到这一点？

What exactly does Control.Invoke(Delegate) do to get the delegate to run on the GUI thread? Furthermore, Its my understanding that invoke will block until the invoked function its done. How does it achieve this?

我想一些好相关细节。我希望能学到一些有趣的事情。

I would like some good gritty details. I'm hoping to learn something interesting.

推荐答案

编辑：控件实现 ISynchronizeInvoke 接口，您可以使用<$ C $做出同样的效果C>的SynchronizationContext 并调用发布 调用。是这样的：

The control implements ISynchronizeInvoke interface, You can make the same effect using the SynchronizationContext and call Post when you call Invoke. something like:

public object Invoke(Delegate method, object[] args)
{
    if (method == null)
    {
        throw new ArgumentNullException("method");
    }

    object objectToGet = null;

    SendOrPostCallback invoker = new SendOrPostCallback(
    delegate(object data)
    {
        objectToGet = method.DynamicInvoke(args);
    });

    _currentContext.Send(new SendOrPostCallback(invoker), method.Target);

    return objectToGet;
}

使用反射

进一步的调查显示，一些本地API调用来实现的调用用途：

private object MarshaledInvoke(Control caller, Delegate method, object[] args, bool synchronous)
{
    int num;
    if (!this.IsHandleCreated)
    {
        throw new InvalidOperationException(SR.GetString("ErrorNoMarshalingThread"));
    }
    if (((ActiveXImpl) this.Properties.GetObject(PropActiveXImpl)) != null)
    {
        IntSecurity.UnmanagedCode.Demand();
    }
    bool flag = false;
    if ((SafeNativeMethods.GetWindowThreadProcessId(new HandleRef(this, this.Handle), out num) == SafeNativeMethods.GetCurrentThreadId()) && synchronous)
    {
        flag = true;
    }
    ExecutionContext executionContext = null;
    if (!flag)
    {
        executionContext = ExecutionContext.Capture();
    }
    ThreadMethodEntry entry = new ThreadMethodEntry(caller, this, method, args, synchronous, executionContext);
    lock (this)
    {
        if (this.threadCallbackList == null)
        {
            this.threadCallbackList = new Queue();
        }
    }
    lock (this.threadCallbackList)
    {
        if (threadCallbackMessage == 0)
        {
            threadCallbackMessage = SafeNativeMethods.RegisterWindowMessage(Application.WindowMessagesVersion + "_ThreadCallbackMessage");
        }
        this.threadCallbackList.Enqueue(entry);
    }
    if (flag)
    {
        this.InvokeMarshaledCallbacks();
    }
    else
    {
        UnsafeNativeMethods.PostMessage(new HandleRef(this, this.Handle), threadCallbackMessage, IntPtr.Zero, IntPtr.Zero);
    }
    if (!synchronous)
    {
        return entry;
    }
    if (!entry.IsCompleted)
    {
        this.WaitForWaitHandle(entry.AsyncWaitHandle);
    }
    if (entry.exception != null)
    {
        throw entry.exception;
    }
    return entry.retVal;
}

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