将基于事件的模式转换为异步 CTP 模式 [英] Convert Event based pattern to async CTP pattern

问题描述

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

如何在 wp7 中将上述代码转换为可等待代码:

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

我也安装了 CTP 和任务并行库.

解决方案

Async CTP 附带了一份文档，该文档描述了如何将每个现有模式调整为基于任务的异步模式.它说基于事件的更可变，但确实举了一个例子:

public static TaskDownloadStringAsync(Uri url){var tcs = new TaskCompletionSource();var wc = new WebClient();wc.DownloadStringCompleted += (s,e) =>{if (e.Error != null) tcs.TrySetException(e.Error);否则如果 (e.Cancelled) tcs.TrySetCanceled();否则 tcs.TrySetResult(e.Result);};wc.DownloadStringAsync(url);返回 tcs.Task;}

被包装的原始函数是 DownloadStringAsync，参数与传递给该函数的参数匹配，DownloadStringCompleted 是被监控的事件.><小时>

(同一文档似乎可以在此处下载 - 以上示例(以及更多描述)来自任务和基于事件的异步模式 (EAP)")

  _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.

解决方案

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)")

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