AsynchronousLINQ

AsynchronousLINQ.cs

static IObservable<string> ReadLineAsObservable(string fileName)
{
    return Observable.Create<string>(async observer =>
    {
        try
        {
            using (var sr = new StreamReader(fileName))
            {
                string s;
                while ((s = await sr.ReadLineAsync().ConfigureAwait(false)) != null)
                {
                    observer.OnNext(s);
                }
            }
            observer.OnCompleted();
        }
        catch (Exception ex)
        {
            observer.OnError(ex);
        }
    });
}

static void Main(string[] args)
{
    ReadLineAsObservable("hogehoge.csv")
        .Select(x => x.Replace("a", "b"))
        .Subscribe(x => Console.WriteLine(x)); // なんかStringWriterに書く:)
            
    Console.ReadLine();
}