aravindg86 says:
TempData["Lines"] = Result.Content.ReadAsAsync<List<Model>>().Result;
TempData["Lines"] = (List<Model>)TempData["Lines"];
Replace the above code with below.
TempData["Lines"] = (List<Model>)Result.Content.ReadAsAsync<List<Model>>().Result;
For more details on passing data from one controller to another controller refer below article.