Silverlight中，处理异步调用

问题描述

我有一些code如下：

I have some code as below:

        foreach (var position in mAllPositions)
        {
                 DoAsyncCall(position);
        }
//I want to execute code here after each Async call has finished

那么，如何能做到上面？
我可以做这样的事情：

So how can I do the above?
I could do something like:

        while (count < mAllPositions.Count)
        {
            //Run my code here
        }

和每个异步调用后增量数由...但是这似乎并不像这样做的一个很好的方式。

and increment count after each Async call is made ... but this doesn't seem like a good way of doing it

有什么建议？有一些设计模式的上述问题，因为我敢肯定，这是一个常见的​​场景？

Any advice? Is there some design pattern for the above problem as i'm sure it's a common scenario?

推荐答案

假设你使用Silverlight和你没有获得信号量，你可能会寻找这样的事情（写在记事本，所以没有承诺以完美的语法）：

Given that you're using Silverlight, and you don't have access to Semaphores, you might be looking for something like this (written in notepad, so no promises as to perfect syntax):

int completedCallCount = 0;
int targetCount = mAllPositions.Count;

using (ManualResetEvent manualResetEvent = new ManualResetEvent(false))
{
    proxy.DoAsyncCallCompleted += (s, e) =>
    {
        if (Interlocked.Increment(ref completedCallCount) == targetCount)
        {
            manualResetEvent.Set();
        }
    };

    foreach (var position in mAllPositions)
    {
        proxy.DoAsyncCall(position);
    }

    // This will wait until all the events have completed.
    manualResetEvent.WaitOne();
}

然而，Silverlight的好处之一强迫你异步加载的数据是，你必须努​​力工作，做一个服务呼叫时锁定UI起来，这是你要什么做code这样的，除非你有在后台线程，我强烈建议你做的运行。直到后台进程完成您可以随时显示请稍候消息。

However, one of the benefits of Silverlight forcing you to asynchronously load data is that you have to work hard to lock the UI up when making a service calls, which is exactly what you're going to do with code like this, unless you have it running on a background thread, which I strongly recommend you do. You can always display a "please wait" message until the background process completes.

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