dotnet/wpf · error · InvalidOperationException

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

Error message

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

What it means

KeyboardDevice.Focus validates that the element being focused is a valid IInputElement (a UIElement, ContentElement, or UIElement3D per InputElement.IsValid). If a non-input element is passed, it throws InvalidOperationException with Invalid_IInputElement.

Solutions

1. Call Focus only with UIElement, ContentElement, or UIElement3D instances
2. Check InputElement.IsValid(element) or 'element is IInputElement' before focusing
3. Find the nearest focusable ancestor (via UIElement/ContentElement) and focus that instead

Example fix

// before
Keyboard.Focus(someDependencyObject);
// after
if (someDependencyObject is IInputElement inputElem)
    Keyboard.Focus(inputElem);

bool focusable = element is IInputElement ie && InputElement.IsValid(ie);

bool IsFocusable(object o) => o is IInputElement;

try { Keyboard.Focus(el); } catch (InvalidOperationException) { /* el is not an IInputElement */ }

When it happens

Trigger: Calling Keyboard.Focus(element) or keyboardDevice.Focus(element) with an object that derives from DependencyObject but does not implement IInputElement properly, or a raw non-element object.

Common situations: Focusing a non-visual DependencyObject (e.g. a free-standing DependencyObject or Binding proxy); confusion between Visual and logical elements in templates; passing a DrawingVisual (not an IInputElement).

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

• SR.Format(SR.Invalid_IInputElement, o.GetType())
• Animation_Invalid_DefaultValue
• Cannot remove signature from read-only file.
• Image_EncoderNoColorContext
• Image_EncoderNoGlobalMetadata

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/de989563bd00af0e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/KeyboardDevice.cs:120

        }

        /// <summary>
        ///     Focuses the keyboard on a particular element.
        /// </summary>
        /// <param name="element">
        ///     The element to focus the keyboard on.
        /// </param>
        public IInputElement Focus(IInputElement element)
        {
            DependencyObject oFocus = null;
            bool forceToNullIfFailed = false;

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

                oFocus = (DependencyObject) element;
            }

            // If no element is given for focus, use the root of the active source.
            if(oFocus == null && _activeSource != null)
            {
                oFocus = _activeSource.RootVisual;
                forceToNullIfFailed = true;
            }

            Focus(oFocus, true, true, forceToNullIfFailed);

            return (IInputElement) _focus;
        }
        private void Focus(DependencyObject focus, bool askOld, bool askNew, bool forceToNullIfFailed)
        {

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