Convert Event based pattern to async CTP pattern

问题:

  _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.

回答1:

The Async CTP came with a document that describes how to adapt each existing pattern to the Task Based Async pattern. It says that the Event based one is more variable, but does give one example:

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;
}

Where the original function that's being wrapped is DownloadStringAsync, the parameters match the parameters being passed to this function, and DownloadStringCompleted is the event that is being monitored.

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(The same document appears to be downloadable here - the above sample (and more description) are from "Tasks and the Event-based Asynchronous Pattern (EAP)")