Describe the bug

Apparently it is possible to use x:Bind to bind to a field in code behind outside a data template. Basically, escaping from the data template in use. Not entirely sure whether this is by design or just a lucky quirk of the XAML compiler and codegen (especially since this is not mentioned anywhere in the docs), but it works.

As a code example:

<UserControl
    x:Class="MyNamespace.Views.MyUserControl"
    xmlns:viewModels="using:MyNamespace.ViewModels"
    models="using:MyNamespace.Models">
    <UserControl.DataContext>
        <viewModels:MyViewModel x:Name="ViewModel"/>
    </UserControl.DataContext>
    <UserControl.Resources>

        <DataTemplate
            x:Name="SomeDataTemplate"
            x:DataTye="models:SomeModelTyppe">

            <!--This works-->
            <TextBlock Text="{x:Bind ViewModel.SomeText}"/>
        </DataTemplate>
    </UserControl.Resources>

    <ListView
        ItemsSource="{x:Bind ViewModel.MyItems}"
        ItemTemplate="{StaticResource SomeDataTemplate}"/>
</UserControl>

You can see how the binding is escaping the data template and just targeting a field in code behind.
The problem with this is that it's extremely fragile and inconsistent:

• x:Bind to a property outside the data template works fine ✅
• x:Bind to that same property but with function binding fails to build ❌
• x:Bind to that same property from a visual state setter crashes at runtime ❌
• x:Bind to that same property with a converter crashes at runtime ❌

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Download this repro
2. Open the solution, run the app

Expected behavior

🤷‍♂️ 🤷‍♂️ 🤷‍♂️

Actual behavior

The binding to the outside field (the view model) works just fine

Screenshots

cc. @MikeHillberg