What causes "Frame not found" in LykosAI/StabilityMatrix?

Include in the FrameCarousel ControlTemplate

LykosAI/StabilityMatrix · error · NullReferenceException

Frame not found

Error message

Frame not found

What it means

FrameCarousel.OnApplyTemplate looks up the template part 'PART_Frame' (a Frame) in the applied template's name scope. If the part is absent, it throws NullReferenceException('Frame not found'), preventing navigation wiring (NavigationPageFactory and initial navigation) from completing.

Solutions

Include <Frame x:Name="PART_Frame"/> in the FrameCarousel ControlTemplate
Verify the applied style/theme is the one intended for FrameCarousel
Preserve the 'PART_Frame' TemplatePart name in any custom template
Log/inspect e.NameScope in OnApplyTemplate to confirm which parts were found

Example fix

// before
<ControlTemplate>
  <Panel/>
</ControlTemplate>
// after
<ControlTemplate>
  <Frame x:Name="PART_Frame"/>
</ControlTemplate>

Defensive patterns

Strategy: validation

Validate before calling

var frame = e.NameScope.Find<Frame>("PART_Frame");
if (frame is null) { Log.Error("PART_Frame missing from FrameCarousel template"); return; }

Type guard

bool HasFramePart(TemplatedControl c) => c.Template != null;

Try / catch

try { frame = e.NameScope.Find<Frame>("PART_Frame")!; }
catch (NullReferenceException ex) { Log.Error(ex, "Frame part not found"); }

Prevention

Always preserve PART_* naming when re-templating
Declare [TemplatePart(nameof(PART_Frame), typeof(Frame))] on the control
Add design-time/template unit tests that apply the template

When it happens

Trigger: The FrameCarousel ControlTemplate lacks an element named 'PART_Frame', the template was overridden with a style that omits the part, or the Frame is not in the templated control's name scope.

Common situations: Custom re-templating of FrameCarousel that forgot the PART_Frame convention; theme assembly mismatch; renaming the part in a refactor.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/dc5cc8ca0c819f3d. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Avalonia/Controls/FrameCarousel.axaml.cs:72

            {
                Effect = SlideNavigationTransitionEffect.FromLeft,
                FromHorizontalOffset = 200
            }
        };
    
    private static readonly FrameNavigationOptions DirectionlessNavigationOptions
        = new()
        {
            TransitionInfoOverride = new SuppressNavigationTransitionInfo()
        };
    
    /// <inheritdoc />
    protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
    {
        base.OnApplyTemplate(e);
        
        frame = e.NameScope.Find<Frame>("PART_Frame") 
                ?? throw new NullReferenceException("Frame not found");
        
        frame.NavigationPageFactory = new FrameNavigationFactory(SourcePageType);

        if (SelectedItem is not null)
        {
            frame.NavigateFromObject(SelectedItem, DirectionlessNavigationOptions);
        }
    }

    protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
    {
        base.OnPropertyChanged(change);

        if (frame is null) return;
        
        if (change.Property == SelectedItemProperty)
        {
            if (change.GetNewValue<object?>() is not { } value) return;

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