Question

我想转换：

blob.UploadFromStream(stream, null, new BlobRequestOptions { RetryPolicy = new LinearRetry(TimeSpan.FromMilliseconds(100), 3) });

到

                Task uploadStreamTask = Task.Factory.FromAsync(
                    blob.BeginUploadFromStream,
                    blob.EndUploadFromStream,
                    stream,
                    null);

我的问题是，如果仅传递给beginUploadFromStream的流参数，则上述工作正常。我无法弄清楚如何让它接受其他参数，如我的第一个例子。

Answer 1

您的代码尝试调用不带任何参数的BeginUploadFromStream-Method的重载 - 但没有这样的重载。为了从需要参数的异步方法创建任务 - 异步模式，请使用FromAsync<>-Method的通用版本。您可以指定Begin-Method需要的参数。

对于Begin / EndUploadFromStream方法，代码如下所示：

Task.Factory.FromAsync<Stream>(blob.BeginUploadFromStream, blob.EndUploadFromStream, stream, null);

但是，既然你需要传递 BlobRequestOptions ，事情也会变得复杂一些：

接受BlobRequestOptions参数的BeginUploadFromStream-Method的重载总共需要四个参数。但是FromAsync＆lt;＆gt;没有过载。接受begin方法的三个以上输入参数的方法。

这就是你可以使用FromAsync＆lt;＆gt;方法虽然：

为ICloudBlob.BeginUploadFromStream创建一个扩展方法，该方法需要两个参数（流和BlobRequestOptions）并将它们正确传递给原始的Begin-Method

public static class Extensions
{
    public static IAsyncResult BeginUploadFromStream(this ICloudBlob blob, Stream source, BlobRequestOptions options, AsyncCallback callback, object state)
    {
        return blob.BeginUploadFromStream(source, 
                                          null, 
                                          options, 
                                          null, 
                                          callback, 
                                          state);
    }
}

使用Async重载来创建任务

Task.Factory
    .FromAsync<Stream, BlobRequestOptions>(blob.BeginUploadFromStream,
                                           blob.EndUploadFromStream, 
                                           stream,
                                           options, 
                                           null);

如果您需要将所有四个参数传递给BeginUploadFromStream-Method，请告诉我。我也知道如何解决这个问题。

<强>更新这是一个四参数Begin方法的解决方案。我期望这个想法能够产生更通用的东西，并且使用更少的反射，但是现在它只适用于没有返回值的EndMethod。

public static Task FromAsync<TArg1, TArg2, TArg3, TArg4>(this TaskFactory factory,
                                                         Func<TArg1, TArg2, TArg3, TArg4, AsyncCallback, object, IAsyncResult> beginMethod,
                                                         Action<IAsyncResult> endMethod,
                                                         TArg1 arg1,
                                                         TArg2 arg2,
                                                         TArg3 arg3,
                                                         TArg4 arg4,
                                                         object state,
                                                         TaskCreationOptions creationOptions)
    {
        // create a promise task that will wait until the async stuff is done
        var constructor = typeof(Task).GetConstructor(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic, null, new Type[] { typeof(object), typeof(TaskCreationOptions), typeof(bool) }, null);
        var promise = constructor.Invoke(new object[] { state, creationOptions, true }) as Task;

        // perform the async pattern method
        try
        {
            IAsyncResult asyncResult = beginMethod(arg1, arg2, arg3, arg4, delegate(IAsyncResult iar)
            {
                if (!iar.CompletedSynchronously)
                {
                    // complete the async pattern
                    endMethod(iar);
                    var mFinish = typeof(Task).GetMethod("Finish", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
                    mFinish.Invoke(promise, new object[] { true });
                }
            }, state);
            if (asyncResult.CompletedSynchronously)
            {
                // complete the async pattern synchronously
                endMethod(asyncResult);
                var mFinish = typeof(Task).GetMethod("Finish", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
                mFinish.Invoke(promise, new object[] { true });
            }
        }
        catch (Exception ex)
        {
        }

        return promise as Task;
    }

将ICloudBlob.UploadFromStream转换为Task.Factory.FromAsync（begin，end，params）

1 个答案: