public async Task SyncWithData()
        {
            JArray data = JArray.Parse(File.ReadAllText(@"Data\work.json"));

            await Users.AddRangeAsync(data.Children <JObject>()["UserId"]
                                      .Values <string>().Distinct()
                                      .Select(user => new User()
            {
                Id = user
            }));

            await Subjects.AddRangeAsync(data.Children <JObject>()["Subject"]
                                         .Values <string>().Distinct()
                                         .Select(subject => new Subject()
            {
                Name = subject
            }));

            await SaveChangesAsync();

            await Subjects.ForEachAsync(subject =>
            {
                subject.Domains = data.Children <JObject>()
                                  .Where(answer => answer["Subject"].ToString() == subject.Name)
                                  .AsJEnumerable()["Domain"].Values <string>().Distinct()
                                  .Select(domain => new Domain()
                {
                    Name = domain
                }).ToList();
            });

            await SaveChangesAsync();

            await Domains.ForEachAsync(domain =>
            {
                domain.LearningObjectives = data.Children <JObject>()
                                            .Where(answer => answer["Domain"].ToString() == domain.Name &&
                                                   answer["Subject"].ToString() == domain.Subject.Name)
                                            .AsJEnumerable()["LearningObjective"].Values <string>().Distinct()
                                            .Select(learningObjective => new LearningObjective()
                {
                    Name = learningObjective
                }).ToList();
            });

            await SaveChangesAsync();

            await LearningObjectives.ForEachAsync(learningObjective =>
            {
                learningObjective.Exercises = data.Children <JObject>()
                                              .Where(answer => answer["LearningObjective"].ToString() == learningObjective.Name)
                                              .AsJEnumerable()
                                              .GroupBy(exercise => exercise["ExerciseId"])
                                              .Select(group => group.First())
                                              .Select(exercise => new Exercise()
                {
                    Id         = exercise["ExerciseId"].ToString(),
                    Difficulty = exercise["Difficulty"].ToString() != "NULL" ? exercise["Difficulty"].Value <double>() : default(double?)
                }).ToList();
            });

            await SaveChangesAsync();

            Answer[] answers = new Answer[data.Children().Count()];

            Parallel.For(0, answers.Length, index => answers[index] = new Answer()
            {
                UserId       = data[index]["UserId"].ToString(),
                ExerciseId   = data[index]["ExerciseId"].ToString(),
                Correct      = data[index]["Correct"].Value <bool>(),
                Id           = data[index]["SubmittedAnswerId"].ToString(),
                SubmitedDate = DateTime.Parse(data[index]["SubmitDateTime"].Value <string>() + 'Z').ToUniversalTime(),
                Progress     = data[index]["Progress"].Value <int>(),
            });
            await Answers.AddRangeAsync(answers);

            await SaveChangesAsync();
        }