public byte[] DownloadCourseMaterialByMatrialId(int MaterialId)
        {
            var    mat      = CourseMaterialManager.GetMaterialByMaterialId(MaterialId);
            string filePath = mat.PathOnServer;

            byte[] fileBytes = System.IO.File.ReadAllBytes(filePath);

            return(fileBytes);
        }
        public byte[] DownloadAsync(int materialid)
        {
            var    mat      = CourseMaterialManager.GetMaterialByMaterialId(materialid);
            string filePath = mat.PathOnServer;// Directory.GetCurrentDirectory() + "\\Uploads\\" + url;
            string fileName = mat.FileName;

            byte[] fileBytes = System.IO.File.ReadAllBytes(filePath);
            //var stream = new FileStream(filePath, FileMode.Open);
            //return File(fileBytes, "application/force-download", fileName);
            return(fileBytes);
        }