How to know when the file was uploaded 100%

I have a functionality of does the following:

The problem:

It puts the link and shows the player, but as the video has not yet uploaded 100% nothing appears in the player. After a few seconds, pressing play will start without any problems.

I keep the video like this:

private void UploadWholeFile(HttpContext context, List<FilesStatus> statuses, 
                              string pre_hash = "")
    {
        for (int i = 0; i < context.Request.Files.Count; i++)
        {
            var file = context.Request.Files[i];

            var fullPath = StorageRoot + pre_hash + Path.GetFileName(file.FileName);


            file.SaveAs(fullPath); // <---- GUARDO AQUI <---------------

            string fullName = Path.GetFileName(file.FileName);
            statuses.Add(new FilesStatus(pre_hash + fullName, file.ContentLength, 
                                          fullPath));
        }
    }

How can I tell when the file has been loaded (this function saves N different files, in the context of this problem there is always only one item for the loop)?