public void SyncTransactions(Action<Exception> callback)
            {
                try
                {
                    TransactionList.Clear();

                    App.Instance.ServiceData.LoadCachedTransactions(error =>
                        {
                            var transList = TransactionList.Where(x => x.ModifiedDate > App.Instance.LastSyncDate).ToObservableCollection();

                            var client = new MainClient();

                            client.SyncTransactionsAsync(transList);

                            client.SyncTransactionsCompleted += async (sender, e) =>
                                {
                                    if (e.Error == null)
                                        await SetupTransactionList(e.Result, true);
                                        
                                    callback(e.Error);
                                };
                        });
                }
                catch (Exception ex)
                {
                    callback(ex);
                }
            }