c# - Convert Event based pattern to async CTP pattern

Question

  _fbClient.GetCompleted += new EventHandler<FacebookApiEventArgs>(OnFetchPageNotification);
  _fbClient.GetAsync(_kNotificationPath, new Dictionary<string, object> { { "access_token", _kPageAccessToken } });

How to convert above code into awaitable code in wp7:

 object = await _fbClient.GetAsync(_kNotificationPath, new Dictionary<string, object> { { "access_token", _kPageAccessToken } });

I have CTP Installed and task parallel library also.

Answer 1

Async CTP 附带一个文档，该文档描述了如何使每个现有模式适应基于任务的异步模式。它说基于事件的事件更多变，但确实给出了一个例子：

public static Task<string> DownloadStringAsync(Uri url)
{
    var tcs = new TaskCompletionSource<string>();
    var wc = new WebClient();
    wc.DownloadStringCompleted += (s,e) =>
    {
        if (e.Error != null) tcs.TrySetException(e.Error);
        else if (e.Cancelled) tcs.TrySetCanceled();
        else tcs.TrySetResult(e.Result);
    };
    wc.DownloadStringAsync(url);
    return tcs.Task;
}

被包装的原始函数是DownloadStringAsync，参数与传递给此函数的参数匹配，并且DownloadStringCompleted是被监视的事件。

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（相同的文档似乎可以在这里下载- 上面的示例（以及更多描述）来自“任务和基于事件的异步模式（EAP）”）