How to download a binary file from Google Drive using C# - google-drive-api

Question

I am using the v3 .Net Google Apis. This seems like it should be a simple task, but nothing I have tried seems to work.
I am able to get the file resource for the file I want by doing this -
var fileRequest = service.Files.Get(fileId);
fileRequest.Fields = "*";
var fileResponse = fileRequest.Execute();
But then I have not been able to actually find a way to download the file. If I use this -
var exportRequest = service.Files.Export(fileResponse.Id, fileResponse.MimeType);
exportRequest.Download(stream);
It returns a 403 Forbidden status with a message stating that Export is only for Google docs.
I've tried this -
var downloadTask = exportRequest.MediaDownloader.DownloadAsync(#"https://docs.google.com/uc?export=download&id=" + fileResponse.Id, file);
downloadTask.Wait();
But that just returns the markup for the page for the user to login. I created the export request using a service account so login should not be required.
Any have a sample of doing this in .Net using the V3 google API?

Answer 1

Ok, I literally got this to work 5 minutes after posting this. Here is what I found works (I know I tried this before and it did not work, but who knows) -
public static async Task DownloadFile(string fileId, DriveService service)
{
var fileRequest = service.Files.Get(fileId);
fileRequest.Fields = "*";
var fileResponse = fileRequest.Execute();
var exportRequest = service.Files.Get(fileResponse.Id);
//you would need to know the file size
var size = fileResponse.Size;
var file = new FileStream(fileResponse.Name, FileMode.OpenOrCreate, FileAccess.ReadWrite);
file.SetLength((long)size);
var response = await fileRequest.DownloadAsync(file);
if (response.Status == Google.Apis.Download.DownloadStatus.Failed)
{
Console.WriteLine("Download failed");
}
}