Working with System.Threading.Tasks.Task<Stream> instead of Stream

Question

I was using a method like below on the previous versions of WCF Web API:

// grab the posted stream
Stream stream = request.Content.ContentReadStream;

// write it to   
using (FileStream fileStream = File.Create(fullFileName, (int)stream.Length)) {

    byte[] bytesInStream = new byte[stream.Length];
    stream.Read(bytesInStream, 0, (int)bytesInStream.Length);
    fileStream.Write(bytesInStream, 0, bytesInStream.Length);
}

But on the preview 6, HttpRequestMessage.Content.ContentReadStream property is gone. I believe that it now should look like this one:

// grab the posted stream
System.Threading.Tasks.Task<Stream> stream = request.Content.ReadAsStreamAsync();

But I couldn't figure out what the rest of the code should be like inside the using statement. Can anyone provide me a way of doing it?

Answer 1

You might have to adjust this depending on what code is happening before/after, and there's no error handling, but something like this:

Task task = request.Content.ReadAsStreamAsync().ContinueWith(t =>
{
    var stream = t.Result;
    using (FileStream fileStream = File.Create(fullFileName, (int) stream.Length)) 
    {
        byte[] bytesInStream = new byte[stream.Length];
        stream.Read(bytesInStream, 0, (int) bytesInStream.Length);
        fileStream.Write(bytesInStream, 0, bytesInStream.Length);
    }
});

If, later in your code, you need to ensure that this has completed, you can call task.Wait() and it will block until this has completed (or thrown an exception).

I highly recommend Stephen Toub's Patterns of Parallel Programming to get up to speed on some of the new async patterns (tasks, data parallelism etc) in .NET 4.