private void BuildPackageInfoFile(long mediaOriginalSize, long mediaZippedSize)
{
PackageInfo pi = new PackageInfo();
pi.PackagePath = this.lessonName + ".zip";
pi.Size = mediaOriginalSize;
pi.ZippedSize = mediaZippedSize;
var mapfileContent = JsonConvert.SerializeObject(pi);
// for every package alwasy use the same package name.
// lesson_221.json
var saveTo = this.constants.LocalMediaPath + @"\lesson_" + lesson.Id + ".pinfo";
MapfileHelper.Save(mapfileContent, saveTo);
}