dotnet/wpf · error · InvalidOperationException

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

Error message

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

What it means

WispStylusDevice.GetPosition (WispStylusDevice.cs:1162) throws InvalidOperationException(SR.Invalid_IInputElement) when the relativeTo argument is non-null and not a valid IInputElement (UIElement, ContentElement, or UIElement3D). GetPosition needs a supported input element to compute the stylus coordinate space.

Solutions

Pass a UIElement, ContentElement, or UIElement3D as relativeTo (e.g. the hosting control instead of the raw visual).
Validate InputElement.IsValid(relativeTo) before calling GetPosition.
Pass null to get coordinates relative to the presentation source and convert manually if needed.

Example fix

// before
var pt = stylusDevice.GetPosition(myDrawingVisual); // throws
// after
if (InputElement.IsValid(myDrawingVisual)) { var pt = stylusDevice.GetPosition(myDrawingVisual); }

Defensive patterns

Strategy: validation

Validate before calling

if (relativeTo != null && !InputElement.IsValid(relativeTo))
    throw new ArgumentException("relativeTo must be UIElement, ContentElement, or UIElement3D");

Type guard

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

Try / catch

try { var pt = stylusDevice.GetPosition(relativeTo); } catch (InvalidOperationException ex) when (ex.Message.Contains("IInputElement")) { /* pass null and transform manually via the hosting UIElement */ }

Prevention

Use the hosting control (UIElement) as the coordinate reference, not raw visuals
Validate relativeTo with InputElement.IsValid before calling
Type reference parameters as UIElement to catch mistakes at compile time

When it happens

Trigger: Calling stylusDevice.GetPosition(relativeTo) with a raw Visual, Visual3D, or other DependencyObject that does not implement IInputElement properly.

Common situations: Passing a DrawingVisual or adorner-layer visual as the reference; variables widened to DependencyObject/Visual during refactoring; passing elements from third-party visual frameworks.

Understand the failure class

Background: "is not a compatible type" / "cannot merge" errors: when a value's type doesn't match what the library requires — this error's family across 65 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/c0433880f49800b1. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Stylus/Wisp/WispStylusDevice.cs:1162

            get
            {
                VerifyAccess();
                return _stylusButtonCollection;
            }
        }

        /////////////////////////////////////////////////////////////////////
        /// <summary>
        ///     Calculates the position of the stylus relative to a particular element.
        /// </summary>
        internal override Point GetPosition(IInputElement relativeTo)
        {
            VerifyAccess();

            // Validate that relativeTo is either a UIElement, a ContentElement or a UIElement3D.
            if (relativeTo != null && !InputElement.IsValid(relativeTo))
            {
                throw new InvalidOperationException(SR.Format(SR.Invalid_IInputElement, relativeTo.GetType()));
            }

            PresentationSource relativePresentationSource = null;

            if (relativeTo != null)
            {
                DependencyObject dependencyObject = relativeTo as DependencyObject;
                DependencyObject containingVisual = InputElement.GetContainingVisual(dependencyObject);
                if (containingVisual != null)
                {
                    relativePresentationSource = PresentationSource.CriticalFromVisual(containingVisual);
                }
            }
            else
            {
                if (_inputSource != null)
                {
                    relativePresentationSource = _inputSource;

View on GitHub (pinned to 81131a70a4)