如果从同一个线程调用，Dispatcher.BeginInvoke 是否会将调用排队？

Question

如果我有这样的电话：

Application.Current.Dispatcher.BeginInvoke(() => someAction);

从 Dispatcher 线程调用的它是排队等待稍后执行还是立即执行，因为它不需要从一个线程切换到另一个线程？

Answer 1

在 Dispatcher 线程中的运行代码和所有其他排队的 BeginInvoke 完成执行后

，它会排队等待执行

Answer 2

does it get queued to be executed later or gets it executed instantly as it does not need to change from one thread to another one?

还在排队。不检查调用该方法的上下文。可以看到in the source:

private void InvokeAsyncImpl(DispatcherOperation operation,
                             CancellationToken cancellationToken)
{
    DispatcherHooks hooks = null;
    bool succeeded = false;

    // Could be a non-dispatcher thread, lock to read
    lock(_instanceLock)
    {
        if (!cancellationToken.IsCancellationRequested &&
            !_hasShutdownFinished && 
            !Environment.HasShutdownStarted)
        {
            // Add the operation to the work queue
            operation._item = _queue.Enqueue(operation.Priority, operation);

            // Make sure we will wake up to process this operation.
            succeeded = RequestProcessing();

            if (succeeded)
            {
                // Grab the hooks to use inside the lock; but we will
                // call them below, outside of the lock.
                hooks = _hooks;
            }
            else
            {
                // Dequeue the item since we failed to request
                // processing for it.  Note we will mark it aborted
                // below.
                _queue.RemoveItem(operation._item);
            }
        } 
    }

    // Rest of method, shortened for brevity.
}

Answer 3

正如其他人指出的那样，它确实需要排队。解决这个问题的一个有用方法是定义：

public void DispatchIfNecessary(Action action) {
    if (!Dispatcher.CheckAccess())
        Dispatcher.Invoke(action);
    else
        action.Invoke();
}

可以这样称呼：

DispatchIfNecessary(() => {
    someAction...
});

如果从同一个线程调用，Dispatcher.BeginInvoke 是否会将调用排队？

Does Dispatcher.BeginInvoke queues the call if it is called from the same thread?

.net

c#

dispatcher

begininvoke