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.