Facebook.FacebookOAuthException: (OAuthException - #100) This authorization code has been used. at Facebook.FacebookClient.ProcessResponse(HttpHelper httpHelper, String responseString, Type resultType, Boolean containsEtag, IList`1 batchEtags) at Facebook.FacebookClient.Api(HttpMethod httpMethod, String path, Object parameters, Type resultType) at Facebook.FacebookClient.Post(String path, Object parameters) at Ookbethod httpMethod, String path, Object parameters, Type resultType) at Facebook.FacebookClient.Post(String path, Object parameters) at Ookbee.Authen.Controllers.LogInController.FacebookCallback(FacebookCallbackModel model)