ReactiveUI in WPF: RoutedViewHost Can't Resolve View - wpf

Question

I recently took up the task of learning how to build an application in WPF, and landed on ReactiveUI as my MVVM framework. I am currently trying to practice implementing the Router in my application, and I'm finding that despite following the examples from "You, I, and ReactiveUI", my RoutedViewHost is not displaying a view, and throws the error:
"System.Exception: 'Couldn't find view for 'LearnReactiveUI.ViewModels.StartupViewModel'.'"
Below is the xaml for my main window (ReactiveWindow), and has a RoutedViewHost as its body
<rxui:ReactiveWindow x:Class="LearnReactiveUI.Views.MainView"
xmlns:rxui="http://reactiveui.net"
xmlns:vms="clr-namespace:LearnReactiveUI.ViewModels"
x:TypeArguments="vms:MainViewModel"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:LearnReactiveUI.Views"
mc:Ignorable="d"
Title="MainView" Height="450" Width="800">
<Grid>
<rxui:RoutedViewHost x:Name="routedViewHost"/>
</Grid>
</rxui:ReactiveWindow>
Here is my MainViewModel class, which creates a RoutingState and then navigates to a new StartupViewModel
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LearnReactiveUI.ViewModels
{
public class MainViewModel : ReactiveObject, IScreen
{
private readonly RoutingState routingState;
public MainViewModel()
{
this.routingState = new RoutingState();
routingState.Navigate.Execute(new StartupViewModel(this));
}
public RoutingState Router => this.routingState;
}
}
And finally here is my code-behind for my MainWindow that binds the Router to the RoutedViewHost
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using LearnReactiveUI.ViewModels;
using System.Reactive.Disposables;
namespace LearnReactiveUI.Views
{
public partial class MainView : ReactiveWindow<MainViewModel>
{
public MainView()
{
InitializeComponent();
this.ViewModel = new MainViewModel();
this.WhenActivated(disposables =>
{
this
.OneWayBind(this.ViewModel, vm => vm.Router, v => v.routedViewHost.Router)
.DisposeWith(disposables);
});
}
}
}
The code for my Startup view is also very simple. Here is the xaml
<rxui:ReactiveUserControl x:Class="LearnReactiveUI.Views.StartupView"
xmlns:rxui="http://reactiveui.net"
xmlns:vms="clr-namespace:LearnReactiveUI.ViewModels"
x:TypeArguments="vms:StartupViewModel"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:LearnReactiveUI.Views"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid>
<Label Content="Startup" HorizontalAlignment="Center"
VerticalAlignment="Center" FontSize="72"/>
</Grid>
</rxui:ReactiveUserControl>
And here is the code for the StartupViewModel
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LearnReactiveUI.ViewModels
{
public class StartupViewModel : ReactiveObject, IRoutableViewModel
{
private IScreen hostScreen;
public StartupViewModel(IScreen hostScreen)
{
this.hostScreen = hostScreen;
}
public string UrlPathSegment => "Startup";
public IScreen HostScreen => this.hostScreen;
}
}
There is no code in the code behind as there are no properties I am binding to the view yet.
My code compiles and I have verified that it will successfully instantiate a MainView and MainViewModel. I am trying to figure out where I went wrong.
Any help is appreciated. Thanks!

Answer 1

You need to register your view and viewModel. Please look at routing example.
In my opinion, this change in the MainViewModel constructor should fix the issue:
public MainViewModel()
{
this.routingState = new RoutingState();
// register view and viewModel
Locator.CurrentMutable.Register(() => new StartupView(), typeof(IViewFor<StartupViewModel>));
routingState.Navigate.Execute(new StartupViewModel(this));
}
#Glenn Watson mentions an important thing. The Locator setup should be done in a bootstrap-like class to allow multiple platform coding and to not break DI. You should look at this when you learn the basics.