dotnet/wpf · error · InvalidEnumArgumentException

InvalidEnumArgumentException("key", (int)key, typeof(Key))

Error message

InvalidEnumArgumentException("key", (int)key, typeof(Key))

What it means

The KeyEventArgs constructor validates that the supplied Key is a keyboard-supported key (Keyboard.IsValidKey). Passing a key outside the valid range or an undefined Key member throws InvalidEnumArgumentException naming parameter 'key'.

Solutions

1. Pass only valid Key values; check Keyboard.IsValidKey(key) before constructing
2. Fix the int-to-Key conversion that produced the invalid value (e.g. off-by-one or wrong virtual-key mapping)
3. For synthetic input, use valid keys from the Input/KeyboardSupport keys tables

Example fix

// before
var args = new KeyEventArgs(kb, src, timestamp, (Key)5000);
// after
Key k = (Key)5000;
if (Keyboard.IsValidKey(k))
    var args = new KeyEventArgs(kb, src, timestamp, k);

bool keyOk = Keyboard.IsValidKey(key);

bool IsValidKey(Key k) => Keyboard.IsValidKey(k);

try { var e = new KeyEventArgs(kb, src, ts, key); } catch (InvalidEnumArgumentException) { /* invalid key from interop */ }

When it happens

Trigger: Constructing new KeyEventArgs(keyboard, inputSource, timestamp, key) with a Key value not in Keyboard's valid key range (e.g. cast from arbitrary int, Key.None misuse, or synthetic key from external input).

Common situations: Raising simulated keyboard events in tests or automation; translating raw scan codes/virtual keys from Win32 interop into Key; corrupt persisted key data.

Understand the failure class

Background: "invalid argument", "unknown mode", "not supported": invalid enum-like argument errors explained — this error's family across 19 libraries.

Related errors

• InvalidEnumArgumentException("key", (int)key, typeof(Key))
• FileAccess value is not valid.
• Invalid priority value.
• origin
• SR.Automation_InvalidEventId

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/fecfc2b25a308a49. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/KeyEventArgs.cs:32

        /// </summary>
        /// <param name="keyboard">
        ///     The logical keyboard device associated with this event.
        /// </param>
        /// <param name="inputSource">
        ///     The input source that provided this input.
        /// </param>
        /// <param name="timestamp">
        ///     The time when the input occurred.
        /// </param>
        /// <param name="key">
        ///     The key referenced by the event.
        /// </param>
        public KeyEventArgs(KeyboardDevice keyboard, PresentationSource inputSource, int timestamp, Key key) : base(keyboard, timestamp)
        {
            ArgumentNullException.ThrowIfNull(inputSource);

            if (!Keyboard.IsValidKey(key))
                throw new System.ComponentModel.InvalidEnumArgumentException("key", (int)key, typeof(Key));

            _inputSource = inputSource;

            _realKey = key;
            _isRepeat = false;

            // Start out assuming that this is just a normal key.
            MarkNormal();
        }

        /// <summary>
        ///     The input source that provided this input.
        /// </summary>
        public PresentationSource InputSource
        {
            get 
            {
                

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