private void ShowRealtorView(object param)
        {
            if (param == null)
            {
                if (Api.ActivateTab("id_name_realtoreditmode_0"))
                {
                    return;
                }
                else
                {
                    RealtorView _newRealtorView = new RealtorView();

                    _newRealtorView.Name    = "id_name_realtoreditmode_0";
                    _newRealtorView.ToolTip = "Добавление риэлтора";

                    _newRealtorView.DataContext = new RealtorViewModel(param as int?);

                    Api.AddTabItem(_newRealtorView);
                    return;
                }
            }

            // else if param is RealtorViewModel

            RealtorViewModel viewModel = param as RealtorViewModel;

            if (viewModel == null)
            {
                return;
            }

            string viewID = "id_name_realtoreditmode_" + viewModel.ID.ToString();

            if (Api.ActivateTab(viewID))
            {
                return;
            }

            // else create new tab

            RealtorView view = new RealtorView();

            view.DataContext = viewModel;

            view.ToolTip = "Риелтор №" + viewModel.ID.ToString();
            view.Name    = viewID;

            Api.AddTabItem(view);
        }
        private void ShowRealtorView(object param)
        {
            if (param == null)
            {
                if (Api.ActivateTab("id_name_realtoreditmode_0"))
                {
                    return;
                }
                else
                {
                    RealtorView _newRealtorView = new RealtorView();

                    _newRealtorView.Name = "id_name_realtoreditmode_0";
                    _newRealtorView.ToolTip = "Добавление риэлтора";

                    _newRealtorView.DataContext = new RealtorViewModel(param as int?);

                    Api.AddTabItem(_newRealtorView);
                    return;
                }
            }

            // else if param is RealtorViewModel

            RealtorViewModel viewModel = param as RealtorViewModel;
            if (viewModel == null) return;

            string viewID = "id_name_realtoreditmode_" + viewModel.ID.ToString();

            if (Api.ActivateTab(viewID)) return;

            // else create new tab

            RealtorView view = new RealtorView();
            view.DataContext = viewModel;

            view.ToolTip = "Риелтор №" + viewModel.ID.ToString();
            view.Name = viewID;

            Api.AddTabItem(view);
        }