public JsonResult AddImage(HttpPostedFileBase image) { var uploadsPath = Server.MapPath(UPLOADS_PATH); var offerImage = new OfferImage(); offerImage.SaveImageTemporarily(image, User.Identity.GetUserId(), uploadsPath); if (Session["images"] == null) { Session["images"] = new List <OfferImage>(); } //offerImage.Id = Guid.NewGuid(); (Session["images"] as List <OfferImage>).Add(offerImage); return(Json(new { thumbPath = offerImage.RelativeThumbnailPath }, contentType: "application/json")); }