Avalonia: FindControl returns null for UserControl lookup.

[milkinllc]

I am getting null when I want to reference UserControl in code behind and using FindControl("Ctrl") to lookup for it. UserControl is just default implementation from Avalonia template.

XAML:
`<Window xmlns="https://github.com/avaloniaui"
xmlns:local="clr-namespace:AvaloniaApplication1;assembly=AvaloniaApplication1"
MinWidth="500" MinHeight="300">

<local:UserControl1 Name="Ctrl"/>

</Window>`

Code:
`namespace AvaloniaApplication1
{
public class MainWindow : Window
{
public MainWindow()
{
this.InitializeComponent();
App.AttachDevTools(this);

        var ctl = this.FindControl<UserControl1>("Ctrl");
    }

    private void InitializeComponent()
    {
        AvaloniaXamlLoader.Load(this);
    }
}

}`

[grokys]

Thanks for the report! This appears to be a problem with named UserControls: seems that becase the UserControl is itself a name scope, the control is getting added to its own name scope and not that of the parent control.

[grokys]

I've been looking into this in WPF and the results are interesting. If I do this (omitting non-relevant attributes etc):

UserControl1.xaml:

<UserControl x:Class="WpfApplication4.UserControl1" Name="foo">

MainWindow1.xaml:

<Window>
    <local:UserControl1/>
</Window>

Then foo is added to UserControl1's name scope but not MainWindows.

If however I do this:

UserControl1.xaml:

<UserControl x:Class="WpfApplication4.UserControl1" Name="foo">

MainWindow1.xaml:

<Window>
    <local:UserControl1 x:Name="bar"/>
</Window>

Then bar is added to both UserControl1s and MainWindows name scope. I think this is because in WPF simply setting a Name on a control doesn't add it to a name scope: you need to call RegisterName.

I didn't want this behavior in Avalonia because I didn't like the fact that there was different behavior between controls created via XAML and controls created in code, but it seems that the behavior has a use in this case.

We have two options here:

1. revert to WPF's behavior (which I'm not even sure OmniXaml supports tbh)
2. register the control in both name scopes

I lean towards 2. though this would cause problems if one were to e.g. include a named UserControl twice in a window.