public NavigationAllSampleViewModel(IEventAggregator eventAggregator)
        {
            this.eventAggregator = eventAggregator;

            Navigation    = NavigationManager.GetNavigationSources("MultipleSubscribersSample");
            this.Commands = new NavigationSourceContainerCommands(Navigation);

            // add sources
            Navigation.AddNewSource(typeof(ViewC), "View C!");
            Navigation.AddNewSource(typeof(ViewD), "View D!");
            Navigation.MoveToLast();

            this.TabControlNavigationSource = new KeyedNavigationSource("TabControl"); // tabControl
            this.ListViewNavigationSource   = new KeyedNavigationSource("ListView");   // listview multiple

            Navigation.Register(TabControlNavigationSource);
            Navigation.Register(ListViewNavigationSource);

            Navigation[0].ClearSourcesOnNavigate = false;
            Navigation[1].ClearSourcesOnNavigate = false;
            Navigation[2].ClearSourcesOnNavigate = false;

            InsertCommand = new DelegateCommand(Insert);
            ClearCommand  = new DelegateCommand(Clear);
        }