UserControl data binding regression in 2.0.0

Description

Binding the DataContext of a UserControl using an ElementName binding worked in 0.9.9, does not work in 2.0.0

Repro steps

MainWindow.xaml

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:local="clr-namespace:ViewModels;assembly=FsEmptyWindowsApp1">
    <StackPanel>
        <TextBox Name="Foo"/>
        <local:TestControl DataContext="{Binding ElementName=Foo, Path=Text}"/>
    </StackPanel>
</Window>

TestControl.xaml

<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
    <TextBox Text="{Binding .}"/>
</UserControl>

Expected behavior

Typing into the TextBox Foo results in the same text in the TestControl.

Actual behavior

TestControl is blank. Binding error in Debug Output is

System.Windows.Data Error: 4 : Cannot find source for binding with reference ‘ElementName=Foo’. BindingExpression:Path=Text; DataItem=null; target element is ‘TestControl’ (Name=‘’); target property is ‘DataContext’ (type ‘Object’)

Known workarounds

None.

Related information

• Windows 8.1
• FsXaml 2.0.0 via nuget
• .NET 4.5

[ReedCopsey]

This has now been solved in 2.1. @mbergin please try https://www.nuget.org/packages/FsXaml.Wpf/2.1.0

It should now work with the ElementName bindings (as well as your x:Reference workaround).

[ruxo]

@ReedCopsey I found that System.Windows.Markup.IComponentConnector plays an important role here (but I don’t know exactly how).

By implementing our UI class with this interface and the binding will work.

Example (sorry, haven’t tried the new library yet):

open RZ.Wpf.CodeBehind

type TestControl() as me =
  inherit UserControl()

  let mutable content_loaded = false

  do (me :> IComponentConnector).InitializeComponent()

  interface IComponentConnector with
    member x.InitializeComponent() =
      if not content_loaded then
          me.InitializeCodeBehind "testcontrol.xaml"

      content_loaded <- true

    member x.Connect(connection_id, target) = content_loaded <- true

(In case you might wonder, this I copied from C# WPF generated code 😄 )