dotnet/wpf · error · InvalidOperationException

SR.Format(SR.Invalid_IInputElement, oldOver.GetType())

Error message

SR.Format(SR.Invalid_IInputElement, oldOver.GetType())

What it means

WispLogic stylus-over (hover) tracking unsubscribes IsEnabled/IsVisible/IsHitTestVisible change handlers from the previous element under the stylus. If oldOver is not UIElement, ContentElement, or UIElement3D, it throws InvalidOperationException naming its type, because over-tracking handler management only supports those element kinds.

Solutions

Ensure hit-test/over targets resolve to UIElement/ContentElement/UIElement3D (wrap DrawingVisuals in a UIElement host)
Verify InputElement.IsValid on elements entering stylus-over tracking
Audit custom hit-test overrides that return non-element visuals directly

Example fix

// before
SetStylusOver(drawingVisual, ...); // unsupported over target
// after
SetStylusOver(FindAncestor<UIElement>(drawingVisual), ...);

Defensive patterns

Strategy: type-guard

Validate before calling

if (element is UIElement || element is ContentElement || element is UIElement3D) { /* safe for stylus-over tracking */ }

Type guard

bool IsSupportedOverElement(IInputElement e) => e is UIElement || e is ContentElement || e is UIElement3D;

Try / catch

try { UpdateStylusOver(newElement); }
catch (InvalidOperationException ex) { Log.Warn("Stylus-over target unsupported", ex); }

Prevention

Ensure hit-test results resolve to supported input elements
Host raw visuals in UIElement wrappers
Avoid custom hit-test overrides that return non-element visuals

When it happens

Trigger: The element previously tracked as StylusDirectlyOver was not a supported input element type — typically after hover state was seeded with a non-element DependencyObject; thrown when stylus-over state changes (PROMOTE/mouse-promotion or actual pen movement).

Common situations: Custom IInputElement hit-test results fed into stylus-over tracking; hover over DrawingVisual-hosted content without a wrapping element; mixed mouse-promotion code paths using non-element visuals.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/e3225ae79ed2de4e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Stylus/Wisp/WispLogic.cs:2175

                    }
                    else if (o is ContentElement ce)
                    {
                        ce.IsEnabledChanged -= _overIsEnabledChangedEventHandler;

                        // NOTE: there are no IsVisible or IsHitTestVisible properties for ContentElements.
                        //
                        // ce.IsVisibleChanged -= _overIsVisibleChangedEventHandler;
                        // ce.IsHitTestVisibleChanged -= _overIsHitTestVisibleChangedEventHandler;
                    }
                    else if (o is UIElement3D uie3D)
                    {
                        uie3D.IsEnabledChanged -= _overIsEnabledChangedEventHandler;
                        uie3D.IsVisibleChanged -= _overIsVisibleChangedEventHandler;
                        uie3D.IsHitTestVisibleChanged -= _overIsHitTestVisibleChangedEventHandler;
                    }
                    else
                    {
                        throw new InvalidOperationException(SR.Format(SR.Invalid_IInputElement, oldOver.GetType())); 
                    }
                }
                if (_stylusOver != null)
                {
                    o = _stylusOver as DependencyObject;
                    if (o is UIElement uie)
                    {
                        uie.IsEnabledChanged += _overIsEnabledChangedEventHandler;
                        uie.IsVisibleChanged += _overIsVisibleChangedEventHandler;
                        uie.IsHitTestVisibleChanged += _overIsHitTestVisibleChangedEventHandler;
                    }
                    else if (o is ContentElement ce)
                    {
                        ce.IsEnabledChanged += _overIsEnabledChangedEventHandler;

                        // NOTE: there are no IsVisible or IsHitTestVisible properties for ContentElements.
                        //
                        // ce.IsVisibleChanged += _overIsVisibleChangedEventHandler;

View on GitHub (pinned to 81131a70a4)