dotnet/wpf · error · InvalidOperationException

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

Error message

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

What it means

PointerLogic.UpdateOverProperty unsubscribes stylus-over event handlers from the previous 'over' element. If oldOver is a DependencyObject but not UIElement, ContentElement, or UIElement3D, InvalidOperationException (SR.Invalid_IInputElement with oldOver.GetType()) is thrown.

Solutions

  1. Ensure elements participating in stylus over-tracking are one of the three supported types
  2. Filter hit-test results to supported element types before feeding input logic
  3. Subclass UIElement/ContentElement/UIElement3D for custom visuals that need stylus hover

Example fix

// before
hitTestResults.ForEach(r => TrackStylusOver(r.Visual)); // may include custom elements
// after
var supported = hitTestResults.Where(r => r.Visual is UIElement || r.Visual is ContentElement || r.Visual is UIElement3D);
foreach (var r in supported) TrackStylusOver(r.Visual);
Defensive patterns

Strategy: type-guard

Validate before calling

if (!(target is UIElement || target is ContentElement || target is UIElement3D)) return; // skip unsupported over targets

Type guard

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

Try / catch

try { TrackStylusOver(element); }
catch (InvalidOperationException) { /* untrack the element and continue */ }

Prevention

When it happens

Trigger: The stylus-over (hover) element becoming an unsupported IInputElement type during over-property update, e.g. hover moving onto a foreign element after a previous supported element, or an unsupported element previously registered as over.

Common situations: Custom hit-test results producing non-standard elements tracked as stylus-over; mixing third-party visual frameworks with WPF stylus input.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/73c523ce65e45501. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Stylus/Pointer/PointerLogic.cs:626

                    }
                    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 element3D)
                    {
                        element3D.IsEnabledChanged -= _overIsEnabledChangedEventHandler;
                        element3D.IsVisibleChanged -= _overIsVisibleChangedEventHandler;
                        element3D.IsHitTestVisibleChanged -= _overIsHitTestVisibleChangedEventHandler;
                    }
                    else
                    {
                        throw new InvalidOperationException(SR.Format(SR.Invalid_IInputElement, oldOver.GetType())); 
                    }
                }
                if (_stylusOver != null)
                {
                    o = _stylusOver as DependencyObject;
                    if (o is UIElement element)
                    {
                        element.IsEnabledChanged += _overIsEnabledChangedEventHandler;
                        element.IsVisibleChanged += _overIsVisibleChangedEventHandler;
                        element.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)