With the great help of Eric Fleck form MSFT we found out that adding DownloadLocation
and Method="Post"
properties making response to be written in DownloadLocation
file. So the valid request is:
var request = new BackgroundTransferRequest(targetUri)
{
DownloadLocation = new Uri(downloadTo, UriKind.Relative),
UploadLocation = new Uri(uploadFrom, UriKind.Relative),
Method = "POST"
};