dotnet/wpf · error · ArgumentException

SR.InputBinding_ExpectedInputGesture (typeof(KeyGesture))

Error message

SR.InputBinding_ExpectedInputGesture (typeof(KeyGesture))

What it means

KeyBinding.Gesture (set) only accepts a KeyGesture; assigning a different InputGesture-derived type (e.g. MouseGesture) throws ArgumentException with SR.InputBinding_ExpectedInputGesture(typeof(KeyGesture)). KeyBinding is a typed specialization of InputBinding, so the gesture type must match.

Solutions

  1. Pass a KeyGesture (e.g. new KeyGesture(Key.S, ModifierKeys.Control)) to KeyBinding.Gesture or its constructor
  2. Use MouseBinding instead of KeyBinding when the gesture is a MouseGesture
  3. Guard with 'is KeyGesture' before assigning

Example fix

// before
keyBinding.Gesture = new MouseGesture(MouseAction.LeftClick);
// after
keyBinding.Gesture = new KeyGesture(Key.S, ModifierKeys.Control);
// or use MouseBinding for mouse gestures
Defensive patterns

Strategy: type-guard

Validate before calling

if (gesture is not KeyGesture) throw new ArgumentException("KeyBinding.Gesture requires a KeyGesture.");

Type guard

static bool IsValidKeyBindingGesture(InputGesture g) => g is KeyGesture;

Try / catch

try { keyBinding.Gesture = gesture; } catch (ArgumentException ex) { /* use MouseBinding for MouseGesture */ }

Prevention

When it happens

Trigger: Assigning KeyBinding.Gesture a MouseGesture, or using the KeyBinding(object command, InputGesture gesture) constructor path where the gesture is not a KeyGesture (the setter is shared).

Common situations: Copy-pasting a MouseBinding setup into a KeyBinding, or reusing a MouseGesture variable in XAML/code where a KeyGesture is required.

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/f6bf3d1fddd72ab4. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Command/KeyBinding.cs:88

        [TypeConverter(typeof(KeyGestureConverter))]
        [ValueSerializer(typeof(KeyGestureValueSerializer))]
        public override InputGesture Gesture
        {
            get
            {
                return base.Gesture as KeyGesture;
            }
            set
            {
                KeyGesture keyGesture = value as KeyGesture;
                if (keyGesture != null)
                {
                    base.Gesture = value;
                    SynchronizePropertiesFromGesture(keyGesture);
                }
                else
                {
                    throw new ArgumentException(SR.Format(SR.InputBinding_ExpectedInputGesture, typeof(KeyGesture)));
                }
            }
        }

        /// <summary>
        ///     Dependency Property for Modifiers
        /// </summary>
        public static readonly DependencyProperty ModifiersProperty =
            DependencyProperty.Register("Modifiers", typeof(ModifierKeys), typeof(KeyBinding), new UIPropertyMetadata(ModifierKeys.None, new PropertyChangedCallback(OnModifiersPropertyChanged)));

        /// <summary>
        ///     Modifiers
        /// </summary>
        public ModifierKeys Modifiers
        {
            get
            {
                return (ModifierKeys)GetValue(ModifiersProperty);

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