A navigation framework and set of UI components for ReactiveUI-based applications across WPF, Avalonia, MAUI, and WinForms.
Overview
CrissCross provides ViewModel-first navigation, hostable navigation surfaces, and a comprehensive WPF UI control set with a strong ReactiveUI focus. It promotes:
ViewModel-first navigation using ReactiveUI�s IViewFor and WhenActivated
Host-based navigation via named ViewModelRoutedViewHost containers
Note: Xamarin.Forms support exists in separate projects but for new apps prefer .NET MAUI.
Core Concepts
CrissCross builds on ReactiveUI to provide ViewModel-first navigation:
IRxObject: Base ViewModel type used throughout CrissCross
IViewFor<TViewModel>: ReactiveUI contract mapping VMs to Views
WhenActivated: ReactiveUI activation lifecycle for Views
ViewModelRoutedViewHost: Navigation host control that manages a navigation stack and view transitions
HostName: A host identifier (string) that allows targeting navigation to a specific host
Navigation lifecycle: WhenNavigating, WhenNavigatedTo, WhenNavigatedFrom via mixins/events
Register your ViewModels and Views with Splat�s Locator or Microsoft.Extensions.DependencyInjection. CrissCross uses the locator to resolve Views for navigation targets.
Quick Start (WPF)
Install packages
CrissCross
CrissCross.WPF
CrissCross.WPF.UI (for controls/themes)
Register ViewModels and Views
public class AppBootstrapper : RxObject
{
public AppBootstrapper()
{
this.BuildComplete(() =>
{
// Example VM/View registrations using Splat
AppLocator.CurrentMutable.RegisterConstant(new MainViewModel());
AppLocator.CurrentMutable.Register<IViewFor<MainViewModel>>(() => new MainView());
AppLocator.CurrentMutable.RegisterConstant(new FirstViewModel());
AppLocator.CurrentMutable.Register<IViewFor<FirstViewModel>>(() => new FirstView());
AppLocator.CurrentMutable.SetupComplete();
});
}
}
Create a navigation host (NavigationWindow)
public partial class MainWindow : NavigationWindow<MainWindowViewModel>
{
public MainWindow()
{
InitializeComponent(); // Ensure x:Name is set on the Window (e.g., "mainWindow")
this.WhenActivated(d =>
{
// Bind back command, etc
NavBack.Command = ReactiveCommand.Create(() => this.NavigateBack(), CanNavigateBack).DisposeWith(d);
// Navigate to a start VM
this.NavigateToView<MainViewModel>();
});
}
}
Navigate from a ViewModel
public class MainViewModel : RxObject
{
public MainViewModel()
{
this.BuildComplete(() =>
{
// Target a specific host by name (Window x:Name)
this.NavigateToView<FirstViewModel>("mainWindow");
});
}
}
Create a View
public partial class MainView : ReactiveUserControl<MainViewModel>
{
public MainView()
{
InitializeComponent();
this.WhenActivated(_ => { /* bindings, commands */ });
}
}
Hosts and Navigation APIs
NavigationWindow (WPF): A Window that exposes a ViewModelRoutedViewHost and transition support
Properties: Transition, NavigateBackIsEnabled
Exposes CanNavigateBack observable and NavigateBack() helper
FluentNavigationWindow (WPF UI): A fluent-styled NavigationWindow with additional title content areas and Transition
NavigationUserControl (WPF UI, Avalonia): A hostable control version of the navigation container (for regions/panels)
The control maintains a NavigationStack and history so you can build rich shell navigation experiences.
Avalonia
NavigationUserControl (host)
ViewModelRoutedViewHost equivalent with CanNavigateBack observable and HostName
Use ReactiveUI�s WhenActivated and Splat for registration as in WPF
public partial class MainUserControl : NavigationUserControl<MainWindowViewModel>
{
public MainUserControl()
{
InitializeComponent();
this.WhenActivated(d =>
{
this.NavigateToView<MainViewModel>();
_NavBack!.Command = ReactiveCommand.Create(() => this.NavigateBack(), this.CanNavigateBack()).DisposeWith(d);
});
}
}
.NET MAUI
MAUI helpers integrate with ReactiveUI.Maui. Register your VMs/Views with DI and navigate using the same NavigateToView/Back helpers where applicable. Prefer this approach over Xamarin.Forms for new apps.
Packages:
CrissCross.MAUI
ReactiveUI.Maui
WinForms
ViewModelRoutedViewHost for WinForms
ReactiveUserControl<TViewModel> usage with WhenActivated
Navigate using the same helper mixins
WPF WebView2 Overlay Host
CrissCross.WPF.WebView2 provides a NavigationWebView that hosts WebView2 while allowing WPF content overlays:
