从我所看到的有关使用具有事件异步模式的Async CTP中看到的代码我应该可以正常工作,var result1 = await tcs1.Task
会阻止,直到clientGetFileList.GetCompleted
被触发。然而,最终发生的是我得到弹回到GetRestoreStream,return GetRestoreStreamAwait().Result
永远不会返回 - 相反,我的应用程序几乎锁定了我。通过Live SDK使用异步/等待
有人可以请向我解释我做错了什么?
protected override Stream GetRestoreStream()
{
if (SkyDriveFolderId != null)
return GetRestoreStreamAwait().Result;
return Stream.Null;
}
private async Task<Stream> GetRestoreStreamAwait()
{
LiveConnectClient clientGetFileList = new LiveConnectClient(_session);
TaskCompletionSource<LiveOperationCompletedEventArgs> tcs1 = new TaskCompletionSource<LiveOperationCompletedEventArgs>();
EventHandler<LiveOperationCompletedEventArgs> d1 = (o, e) => { tcs1.TrySetResult(e); };
clientGetFileList.GetCompleted += d1;
clientGetFileList.GetAsync(SkyDriveFolderId + "/files");
var result1 = await tcs1.Task;
clientGetFileList.GetCompleted -= d1;
// ... method continues for a while
}
更新:此代码位似乎看透一路移动,但task.Start()
扔关的InvalidOperationException
所以我从来没有真正得到末尾的流。将它封装在try/catch中并不会改变任何内容 - 如果没有try/catch,则InvalidOperationException将被进一步捕获到堆栈中,而操作愉快地忽略了它的结果永远不会被使用;有了它,task.Result
冻结的东西就像上面的代码一样肯定。
protected override Stream GetRestoreStream()
{
if (SkyDriveFolderId != null)
{
var task = GetRestoreStreamImpl();
task.Start();
return task.Result;
}
return Stream.Null;
}
private async Task<Stream> GetRestoreStreamImpl()
{
var getResult = await GetTaskAsync(SkyDriveFolderId + "/files");
List<object> data = (List<object>)getResult["data"];
foreach (IDictionary<string, object> dictionary in data)
{
if (dictionary.ContainsKey("name") && (string)dictionary["name"] == BackupFileName)
{
if (dictionary.ContainsKey("id"))
{
SkyDriveFileId = (string)dictionary["id"];
break;
}
}
}
if (String.IsNullOrEmpty(SkyDriveFileId))
{
MessageBox.Show("Restore failed: could not find backup file", "Backup", MessageBoxButton.OK);
return Stream.Null;
}
return await DownloadTaskAsync(SkyDriveFileId + "/content");
}
private Task<IDictionary<string,object>> GetTaskAsync(string path)
{
var client = new LiveConnectClient(_session);
var tcs = new TaskCompletionSource<IDictionary<string, object>>();
client.GetCompleted += (o, e) =>
{
if (e.Error != null)
tcs.TrySetException(e.Error);
else if (e.Cancelled)
tcs.TrySetCanceled();
else
tcs.TrySetResult(e.Result);
};
client.GetAsync(path);
return tcs.Task;
}
private Task<Stream> DownloadTaskAsync(string path)
{
var client = new LiveConnectClient(_session);
var tcs = new TaskCompletionSource<Stream>();
client.DownloadCompleted += (o, e) =>
{
if (e.Error != null)
tcs.TrySetException(e.Error);
else if (e.Cancelled)
tcs.TrySetCanceled();
else
tcs.TrySetResult(e.Result);
};
client.DownloadAsync(path);
return tcs.Task;
}
看起来,微软已经有一个Live Connect SDK的'async' /'await'示例,并且我的Google-fu需要一些工作。该示例位于https://github.com/liveservices/LiveSDK/tree/master/Samples/WindowsPhone/LiveSDKAsyncAwaitSample,并且与我尝试的方式有所不同。 – 2012-04-05 01:30:22