C#5 ReadAsync和迭代器

Question

我试图将下面的类转换为懒惰返回一个文件.

public class ObservableFile2 : IObservable<string>
{
    private readonly IObservable<string> subject;

    public ObservableFile2(string fileName)
    {
        subject = Observable.Using<string, StreamReader>
            (
                () => new StreamReader(new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read)),
                streamReader => ObserveLines(streamReader)
            );
    }

    private IObservable<string> ObserveLines(StreamReader streamReader)
    {
        return ReadLines(streamReader).ToObservable();
    }

    private IEnumerable<string> ReadLines(StreamReader streamReader)
    {
        while (!streamReader.EndOfStream)
        {
            yield return streamReader.ReadLine();
        }
    }        

    public IDisposable Subscribe(IObserver<string> observer)
    {
        return subject.Subscribe(observer);
    }
}

我现在正试图将其转换为使用

StreamReader.ReadLineAsync() 

甚至更好的是将数据分块,即

await SourceStream.ReadAsync(buffer, 0, chunkSize). 

我似乎没有掌握如何包装和解包任务

欢迎提供援助.

谢谢

Answer 1

我不是 Rx大师,所以可能有比我的答案更好的方法.

我相信这应该可以使用async-enabled Create:

public static class ObservableFile2
{
  public static IObservable<string> Create(string fileName)
  {
    return Observable.Create<string>(async (subject, token) =>
    {
      try
      {
        using (var streamReader = new StreamReader(new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read))
        {
          while (true)
          {
            token.ThrowIfCancellationRequested();
            var line = await streamReader.ReadLineAsync();
            if (line == null)
            {
              subject.OnCompleted();
              return;
            }
            subject.OnNext(line);
          }
        }
      }
      catch (Exception ex)
      {
        subject.OnError(ex);
      }
    });
  }
}