adding WindowsFormsHost control to MainWindow causes to crash the exe - wpf

Question

I'm using WPF in F# via FsXaml. The MainWindow works, until I add a WindowsFormsHost control, at which point it will crash with the following error when executed:
Unhandled Exception: System.Xaml.XamlObjectWriterException: Cannot create unknown type '{http://schemas.microsoft.com/winfx/2006/xaml/presentation}WindowsFormsHost'.
at System.Xaml.XamlObjectWriter.WriteStartObject(XamlType xamlType)
at System.Xaml.XamlWriter.WriteNode(XamlReader reader)
at FsXaml.InjectXaml.from$cont#37(String file, Object root, Stream resStream, Unit unitVar)
at FsXaml.InjectXaml.from(String file, Object root)
at Program.Win.InitializeComponent()
at Program.Win..ctor()
Is there anything I need to add the xaml or the app to recognize the winformshost? The C# generated xaml works in a C# app. The F# app works if there is no winformshost inside it. The difference between the C# and F# xamls is the x-local namespace reference.
The MainWindow.xaml:
<Window
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"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Button x:Name="button" Content="Button" HorizontalAlignment="Left" Height="124" VerticalAlignment="Top" Width="217"/>
<WindowsFormsHost HorizontalAlignment="Left" Height="123" Margin="49,171,0,0" VerticalAlignment="Top" Width="394"/>
</Grid>
</Window>
The App.xaml
<Application
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>
</Application.Resources>
</Application>
Program.fs:
open System
open System.Windows
open FsXaml
open Microsoft.FSharp.Control
open System.Windows.Forms
open System.Windows.Forms.Integration
open FSharp.Charting
open FSharp.Charting.ChartTypes
type App = XAML<"App.xaml">
type Win = XAML<"MainWindow.xaml">
[<STAThread>]
[<EntryPoint>]
let main _ =
let app = App()
let win = Win()
win.button.Content <- "Click!"
win.button.MouseRightButtonDown.Add (fun _ -> MessageBox.Show("OK") |> ignore)
app.Run win |> ignore
0

Answer 1

Try explicitly adding the namespace (using clr-namespace), the same way you would for the winforms controls themselves - just use System.Windows.Forms.Integration. I assume that isn't included in the default XAML namespace :)
xmlns:wfi="clr-namespace:System.Windows.Forms;assembly=WindowsFormsIntegration"