c# - 循环中委托(delegate)的异步调用

Question

我需要为同一个函数异步调用多个委托(delegate)。问题是我应该如何对待回调函数？我们有几个委托(delegate)在运行，所以 CallbackMethod 并不意味着所有异步委托(delegate)都已完成。

AsyncMethodCaller c = new AsyncMethodCaller(instance.dummyMethod);
for (int i = 0; i < 100; i++)
    {
        IAsyncResult res = c.BeginInvoke(5000,
            out dummy, 
            new AsyncCallback(CallbackMethod),
            "executed on thread {0}, with result value \"{1}\".");
}

Answer 1

我会考虑使用 TPL 提供的 Task .

var task1 = Task.Run(() => instance.dummyMethod)
   .ContinueWith((completedTask) => Console.WriteLine("Each callback here. Result: " + completedTask.Result));

// Blocks calling thread until all tasks are done.
Task.WaitAll(new [] { task1, task2 });

WaitAll 都确保所有Task 在继续主线程之前完成。以上允许您实现单独的回调。

当所有异步方法完成时，或者使用单个回调:

Task.Factory.ContinueWhenAll(new [] { task1, task2 },
   (allTasks) => Console.WriteLine("Callback when all are done."));