对Control.Invoke()的实现感到好奇

Question

Control.Invoke(Delegate)究竟做了什么来让代理在GUI线程上运行？此外,我的理解是invoke将阻塞,直到被调用的函数完成.它是如何实现这一目标的？

我想要一些好的细节.我希望学到一些有趣的东西.

Answer 1

编辑：该控件实现接口，您可以在调用时使用和 来ISynchronizeInvoke实现相同的效果。就像是：SynchronizationContextPostInvoke

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 Reflector 进行的进一步调查表明，它Invoke使用一些本机 API 调用来实现：

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;
}