DropBox API calls Uploading a Zero byte file

Question

I am trying to upload a file to dropbox using rest calls but it is not uploading the actual file, it is uploading a zero byte file.

Please check the code and let me know if i am missing something.

var task = Task.Run((Func<Task<int>>)OrderExtractUsecase.DropBox);
task.Wait();
int x = task.Result;

Dropbox task Code is:

static async Task<int> DropBox()
    {
        try
        {
            Dropbox_Utility objDropBox = new Dropbox_Utility("<accessid>");
            foreach (string temp in fileList)
            {
                await objDropBox.Upload("/Assist", temp);
            }
            return 1;
        }
        catch(Exception ex)
        {
            return -1;
        }
    }

Upload task code is:

    public async Task<string> Upload(string folder, string filefullpath)
    {
         string filename = string.Empty;
         string fileID = string.Empty;
         try
         {
            filename = Path.GetFileName(filefullpath);

            using (FileStream fileStream = File.OpenRead(filefullpath))
            {
                using (MemoryStream memoryStream = new MemoryStream())
                {
                    fileStream.CopyTo(memoryStream);
                    var response = await dbx.Files.UploadAsync(folder + "/" + filename, WriteMode.Overwrite.Instance, body: memoryStream);
                    fileID = response.Id;
                }
            }
        }
        catch (Exception ex) { throw; }
        finally { }
        return fileID;
    }

Answer 1

As awh112 mentioned, you need to reset the position of memoryStream. After the copyTo, the Position of memoryStream is the length of the file. For that reason, your code will upload a zero byte file. I've confirmed as much with the following:

fileStream.CopyTo(memoryStream);
Console.WriteLine(memoryStream.Position);
var response = await dbx.Files.UploadAsync(folder + "/" + filename, WriteMode.Overwrite.Instance, body: memoryStream);
Console.WriteLine((response as FileMetadata).Size);

That prints: (in my case, my test file is just 12 bytes long)

12
0

You can rewind it like this:

fileStream.CopyTo(memoryStream);
Console.WriteLine(memoryStream.Position);
memoryStream.Position = 0;
Console.WriteLine(memoryStream.Position);
var response = await dbx.Files.UploadAsync(folder + "/" + filename, WriteMode.Overwrite.Instance, body: memoryStream);
Console.WriteLine((response as FileMetadata).Size);

That prints:

12
0
12

The resulting uploaded file then contains the expected contents.