dotnet/wpf · error · InvalidEnumArgumentException

InvalidEnumArgumentException("actions", (int)actions…

Error message

InvalidEnumArgumentException("actions", (int)actions, typeof(RawMouseActions))

What it means

The RawMouseInputReport constructor validates the actions parameter against IsValidRawMouseActions and throws InvalidEnumArgumentException when the value is not a valid RawMouseActions combination. Only defined mouse-report actions (ReportMove, AbsoluteMove, ReportWheel, RelativeMove, Activate, etc.) may be supplied; a null state is allowed, but the actions value must still be valid.

Solutions

Build actions from named RawMouseActions flags only; never cast unchecked ints.
Check the value with IsValidRawMouseActions/Enum.IsDefined-style validation before constructing.
Ensure flag combinations are legal (e.g. don't combine AbsoluteMove with RelativeMove improperly).
Update interop mappings after upgrading WPF versions in case the enum changed.

Example fix

// before
var actions = (RawMouseActions)rawFlags;
var report = new RawMouseInputReport(..., actions, x, y, wheel, extra); // throws for bad flags

// after
var actions = move ? RawMouseActions.AbsoluteMove : RawMouseActions.ReportMove;
var report = new RawMouseInputReport(..., actions, x, y, wheel, extra);

Defensive patterns

Strategy: validation

Validate before calling

static bool IsValidRawMouseActionsValue(RawMouseActions a) =>
    Enum.IsDefined(typeof(RawMouseActions), a);
// then:
if (!IsValidRawMouseActionsValue(actions))
    actions = RawMouseActions.AbsoluteMove;

Type guard

bool TryGetMouseActions(int raw, out RawMouseActions actions)
{
    actions = (RawMouseActions)raw;
    return Enum.IsDefined(typeof(RawMouseActions), actions);
}

Try / catch

try
{
    var report = new RawMouseInputReport(src, mode, ts, actions, x, y, wheel, extra);
}
catch (InvalidEnumArgumentException ex)
{
    Log($"Invalid RawMouseActions: {ex}");
}

Prevention

Build actions from named flags (AbsoluteMove, ReportMove, ReportWheel, Activate).
Never pass raw interop integers unchecked into the enum.
Keep legal flag combinations (don't mix Absolute and Relative moves).
Re-verify mappings after any WPF version upgrade.

When it happens

Trigger: Passing an undefined or illegal combination of RawMouseActions flags to the constructor — typically from casting raw integer mouse data, setting AbsoluteMove without valid coordinates semantics, or passing 0.

Common situations: Custom mouse-input synthesis, automation/testing frameworks generating RawMouseInputReport, interop layers translating Win32 mouse messages without proper enum mapping.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/ad1fa7b93337557a. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/RawMouseInputReport.cs:55

        /// </param>
        /// <param name="wheel">
        ///     If wheel delta being reported.
        /// </param>
        /// <param name="extraInformation">
        ///     Any extra information being provided along with the input.
        /// </param>
        public RawMouseInputReport(
            InputMode mode,
            int timestamp, 
            PresentationSource inputSource,
            RawMouseActions actions, 
            int x, 
            int y, 
            int wheel, 
            IntPtr extraInformation) : base(inputSource, InputType.Mouse, mode, timestamp)
        {
            if (!IsValidRawMouseActions(actions))
                throw new System.ComponentModel.InvalidEnumArgumentException("actions", (int)actions, typeof(RawMouseActions));

            /* we pass a null state from MouseDevice.PreProcessorInput, so null is valid value for state */
            _actions = actions;
            _x = x;
            _y = y;
            _wheel = wheel;
            _extraInformation = extraInformation;
        }

        /// <summary>
        ///     Read-only access to the set of actions that were reported.
        /// </summary>
        public RawMouseActions Actions {get {return _actions;}}

        /// <summary>
        ///     Read-only access to the horizontal position that was reported.
        /// </summary>
        public int X {get {return _x;}}

View on GitHub (pinned to 81131a70a4)