public static Task SetTrainingExerciseTask(AuthData authData, TrainingExerciseVM item)
        {
            var client = WebService.Instance.WS;
            var tcs = new TaskCompletionSource<TrainingDayVM>();

            EventHandler<SetTrainingExerciseCompletedEventArgs> handler = null;
            handler = (sender, e) =>
            {
                client.SetTrainingExerciseCompleted -= handler;

                if (e.Error != null)
                {
                    tcs.SetException(e.Error);
                }
                else
                {
                    tcs.SetResult(e.Result);
                }
            };

            client.SetTrainingExerciseCompleted += handler;
            client.SetTrainingExerciseAsync(authData, item);

            return tcs.Task;
        }
        public static Task<ObservableCollection<TrainingExerciseVM>> GetExerciseHistoryTask(AuthData authData, TrainingExerciseVM trainingExerciseItem)
        {
            var client = WebService.Instance.WS;
            var tcs = new TaskCompletionSource<ObservableCollection<TrainingExerciseVM>>();

            EventHandler<GetExerciseHistoryCompletedEventArgs> handler = null;
            handler = (sender, e) =>
            {
                client.GetExerciseHistoryCompleted -= handler;

                if (e.Error != null)
                {
                    tcs.SetException(e.Error);
                }
                else
                {
                    tcs.SetResult(e.Result);
                }
            };

            client.GetExerciseHistoryCompleted += handler;
            client.GetExerciseHistoryAsync(authData, trainingExerciseItem);

            return tcs.Task;
        }