public static EmployeeWindow CreateEmployeeWindow(Window currentWindowView, EmployeeWindow employeeView, EmployeeViewModel workerVM, MiddleClassModel MiddleModel)
        {
            try
            {
                // ensure only one view is loaded, and the same one remains open for multiple requests
                employeeView = employeeView ?? new EmployeeWindow();

                if (!employeeView.IsLoaded)
                {
                    employeeView.Close();
                    employeeView             = new EmployeeWindow();
                    workerVM.MiddleModel     = MiddleModel;
                    employeeView.DataContext = workerVM;
                    currentWindowView.Close();
                }

                employeeView.Show();
                return(employeeView);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error", ex.Message);
                //Application.Current.Shutdown();
                return(employeeView);
            }
        }
        private void Application_Startup(object sender, StartupEventArgs e)
        {
            try
            {
                AccountViewModel    accountVM      = new AccountViewModel();
                MainViewModel       mainVM         = new MainViewModel();
                ContractViewModel   contractVM     = new ContractViewModel();
                ClientViewModel     clientVM       = new ClientViewModel();
                RealEstateViewModel realEstateVM   = new RealEstateViewModel();
                EmployeeViewModel   employeeVM     = new EmployeeViewModel();
                MainWindow          mainView       = null;
                AccountWindow       accountView    = null;
                ContractWindow      contractView   = null;
                ClientWindow        clientView     = null;
                RealEstateWindow    realEstateView = null;
                EmployeeWindow      employeeView   = null;
                // open the Users screen
                mainVM.ShowContractScreenAction += () =>
                {
                    contractView = NavigationWindows.CreateContractWindow(mainView, contractView, contractVM, mainVM.MiddleModel);
                };

                mainVM.ShowClientScreenAction += () =>
                {
                    clientView = NavigationWindows.CreateUserWindow(mainView, clientView, clientVM, mainVM.MiddleModel);
                };

                mainVM.ShowRealEstateScreenAction += () =>
                {
                    realEstateView = NavigationWindows.CreateRealEstateWindow(mainView, realEstateView, realEstateVM, mainVM.MiddleModel);
                };

                mainVM.ShowWorkerScreenAction += () =>
                {
                    employeeView = NavigationWindows.CreateEmployeeWindow(mainView, employeeView, employeeVM, mainVM.MiddleModel);
                };
                accountVM.ShowMainScreenAction += () =>
                {
                    mainView = NavigationWindows.CreateMainWindow(accountView, mainView, mainVM, accountVM.MiddleModel);
                };

                clientVM.ShowContractScreenAction += () =>
                {
                    contractView = NavigationWindows.CreateContractWindow(clientView, contractView, contractVM, clientVM.MiddleModel);
                };
                clientVM.ShowMainScreenAction += () =>
                {
                    mainView = NavigationWindows.CreateMainWindow(clientView, mainView, mainVM, clientVM.MiddleModel);
                };
                realEstateVM.ShowContractScreenAction += () =>
                {
                    contractView = NavigationWindows.CreateContractWindow(realEstateView, contractView, contractVM, realEstateVM.MiddleModel);
                };
                realEstateVM.ShowMainScreenAction += () =>
                {
                    mainView = NavigationWindows.CreateMainWindow(realEstateView, mainView, mainVM, realEstateVM.MiddleModel);
                };
                contractVM.ShowMainScreenAction += () =>
                {
                    mainView = NavigationWindows.CreateMainWindow(contractView, mainView, mainVM, contractVM.MiddleModel);
                };
                contractVM.ShowUserScreenAction += () =>
                {
                    clientView = NavigationWindows.CreateUserWindow(contractView, clientView, clientVM, contractVM.MiddleModel);
                };
                contractVM.ShowRealEstateScreenAction += () =>
                {
                    realEstateView = NavigationWindows.CreateRealEstateWindow(contractView, realEstateView, realEstateVM, contractVM.MiddleModel);
                };
                employeeVM.ShowMainScreenAction += () =>
                {
                    mainView = NavigationWindows.CreateMainWindow(employeeView, mainView, mainVM, employeeVM.MiddleModel);
                };
                employeeVM.ShowContractScreenAction += () =>
                {
                    contractView = NavigationWindows.CreateContractWindow(employeeView, contractView, contractVM, employeeVM.MiddleModel);
                };
                //mainView = new MainWindow();
                //mainView.DataContext = mainVM;
                //mainView.Show();

                accountView             = new AccountWindow();
                accountView.DataContext = accountVM;
                accountView.Show();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error", ex.Message);
                Application.Current.Shutdown();
            }
        }