Current implementation of FilesResource.GetRequest's DownloadAsync with range parameter doesn't expose a way to modify used MediaDownloader.

Hi,

The current implementation of Google.Apis.Drive.v3.FilesResource.GetRequest’s DownloadAsync with a range parameter is the following:

        public virtual Google.Apis.Download.IDownloadProgress DownloadRange(System.IO.Stream stream, System.Net.Http.Headers.RangeHeaderValue range)
        {
            var mediaDownloader = new Google.Apis.Download.MediaDownloader(Service);
            mediaDownloader.Range = range;
            return mediaDownloader.Download(this.GenerateRequestUri(), stream);
        }

        /// <summary>Asynchronously download a range of the media into the given stream.</summary>
        public virtual System.Threading.Tasks.Task<Google.Apis.Download.IDownloadProgress> DownloadRangeAsync(System.IO.Stream stream,
            System.Net.Http.Headers.RangeHeaderValue range,
            System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken))
        {
            var mediaDownloader = new Google.Apis.Download.MediaDownloader(Service);
            mediaDownloader.Range = range;
            return mediaDownloader.DownloadAsync(this.GenerateRequestUri(), stream, cancellationToken);
        }

https://github.com/googleapis/google-api-dotnet-client/blob/87fd4114950f268002345552614effb3843470c8/Src/Generated/Google.Apis.Drive.v3/Google.Apis.Drive.v3.cs#L2391

The problem is we cannot modify the newly created mediaDownloader, for example to use ChunkSize and/or ProgressChanged event. In fact, it gives the false impression that the methods behave similar to the “non-ranged” which is not the case.

One possible workaround is to derive from GetRequest, something like this:

    public class GetRequest2 : FilesResource.GetRequest
    {
        public event Action<IDownloadProgress> ProgressChanged;

        public GetRequest2(IClientService service, string fileId)
            : base(service, fileId)
        {
        }

        public override Task<IDownloadProgress> DownloadRangeAsync(Stream stream, RangeHeaderValue range, CancellationToken cancellationToken = default)
        {
            var downloader = new MediaDownloader(Service);
            downloader.ChunkSize = 0x10000;
            downloader.Range = range;
            downloader.ProgressChanged += (a) => ProgressChanged?.Invoke(a);
            return downloader.DownloadAsync(GenerateRequestUri(), stream, cancellationToken);
        }
    }

[jskeet]

Okay, I can see a few options here. It might be simplest to generate new overloads:

public IDownloadProgress Download(Stream stream, Action<MediaDownloader> downloaderModifier)
public Task<IDownloadProgress> DownloadAsync(Stream stream, Action<MediaDownloader> downloaderModifier)

That allows more freedom in general. Will discuss with other team members.

[jskeet]

We’ve now implemented that plan in the 1.51.0 clients.