RoutedViewHost causes designer error in VisualStudio 2012

[swsnr]

The following MainWindow.xaml causes a "System.Remote.Remoting.RemotingException" when viewed in the designer of VisualStudio 2012:

<Window x:Class="MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:routing="clr-namespace:ReactiveUI.Routing;assembly=ReactiveUI.Routing_Net45"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <routing:RoutedViewHost x:Name="ViewHost" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
    </Grid>
</Window>

[jordansjones]

This is related to commit 4d71c9d

Here is a stack trace:

Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteException
An OnError occurred on an object (usually ObservableAsPropertyHelper) that would break a binding or command. To prevent this, Subscribe to the ThrownExceptions property of your objects
   at ReactiveUI.RxApp.<>c__DisplayClass9.<.cctor>b__2() in y:\HomeDirectoryStorage\SkyDrive\ReactiveUI_External\ReactiveUI\RxApp.cs:line 80
   at System.Reactive.Concurrency.Scheduler.Invoke(IScheduler scheduler, Action action)
   at System.Reactive.Concurrency.ScheduledItem`2.InvokeCore()
   at System.Reactive.Concurrency.EventLoopScheduler.Run()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteException
Exception has been thrown by the target of an invocation.
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
   at ReactiveUI.Reflection.<>c__DisplayClass29.<.cctor>b__1e(Object y) in y:\HomeDirectoryStorage\SkyDrive\ReactiveUI_External\ReactiveUI\Reflection.cs:line 66
   at ReactiveUI.Reflection.TryGetValueForPropertyChain[TValue](TValue& changeValue, Object current, String[] propNames) in y:\HomeDirectoryStorage\SkyDrive\ReactiveUI_External\ReactiveUI\Reflection.cs:line 247
   at ReactiveUI.ObservedChangedMixin.TryGetValue[TSender,TValue](IObservedChange`2 This, TValue& changeValue) in y:\HomeDirectoryStorage\SkyDrive\ReactiveUI_External\ReactiveUI\ObservedChangedMixin.cs:line 45
   at ReactiveUI.ObservedChangedMixin.fillInValue[TSender,TValue](IObservedChange`2 This) in y:\HomeDirectoryStorage\SkyDrive\ReactiveUI_External\ReactiveUI\ObservedChangedMixin.cs:line 54
   at ReactiveUI.ReactiveNotifyPropertyChangedMixin.<nestedObservedChanges>b__1(IObservedChange`2 x) in y:\HomeDirectoryStorage\SkyDrive\ReactiveUI_External\ReactiveUI\ReactiveNotifyPropertyChangedMixin.cs:line 139
   at System.Reactive.Linq.Observαble.Select`2._.OnNext(TSource value)

Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteException
The calling thread cannot access this object because a different thread owns it.
   at System.Windows.Threading.Dispatcher.VerifyAccess()
   at System.Windows.DependencyObject.GetValue(DependencyProperty dp)
   at ReactiveUI.Routing.RoutedViewHost.get_Router() in y:\HomeDirectoryStorage\SkyDrive\ReactiveUI_External\ReactiveUI.Routing\RoutedViewHost.cs:line 33

[anaisbetts]

@jordansjones Good work tracking this down. Can you submit a PR to fix it? I would just disable the WhenAny or exit early in design mode, there should be a method on RxApp to tell you whether you're in Design Mode or not

[DamianReeves]

Any plan on putting this out in a fix for ReactiveUI 4.5?

[anaisbetts]

@DamianReeves This got merged into master, it should show up in the next 4.x release soon