public OverViewController(IntPtr handle)
     : base(handle)
 {
     viewModel = securitiesViewModel;
 }
        public override void ViewDidLoad()
        {
            base.ViewDidLoad ();
            this.NavigationItem.HidesBackButton = true;

            this.SegmentedController.ValueChanged += (sender, e) => {
                switch (SegmentedController.SelectedSegment) {
                case 0:
                    {
                        viewModel = securitiesViewModel;
                        this.SecuritiesTableView.ReloadData ();
                        break;
                    }
                case 1:
                    {
                        viewModel = depositoriesViewModel;
                        this.SecuritiesTableView.ReloadData ();
                        break;
                    }
                case 2:
                    {
                        viewModel = historyViewModel;
                        this.SecuritiesTableView.ReloadData ();
                        break;
                    }
                }
            };

            tableViewController.TableView = SecuritiesTableView;
            tableViewController.RefreshControl = refreshControl;
            refreshControl.ValueChanged += async (sender, e) => {
                refreshControl.BeginRefreshing ();
                await updateModel.UpdateTransactions ();
                this.SecuritiesTableView.ReloadData ();
                refreshControl.EndRefreshing ();
            };

            this.SecuritiesTableView.WeakDataSource = this;
            this.SecuritiesTableView.WeakDelegate = this;
            this.SecuritiesTableView.TableFooterView = new UIView (RectangleF.Empty);
        }