dotnet/wpf · error · InvalidEnumArgumentException

InvalidEnumArgumentException("value", (int) value…

Error message

InvalidEnumArgumentException("value", (int) value, typeof(BindingMode))

What it means

The Binding.Mode setter converts the BindingMode value via FlagsFrom; if the result is BindingFlags.IllegalInput the value is not a valid BindingMode, and an InvalidEnumArgumentException is thrown for parameter 'value'. This can also happen when an out-of-range integer is cast to the enum.

Solutions

Assign only defined BindingMode members (OneWay, TwoWay, OneWayToSource, OneTime, Default).
Validate with Enum.IsDefined(typeof(BindingMode), value) before casting/assigning.
Sanitize persisted values at load time, defaulting to BindingMode.Default.

Example fix

// before
binding.Mode = (BindingMode)rawInt;
// after
binding.Mode = Enum.IsDefined(typeof(BindingMode), rawInt) ? (BindingMode)rawInt : BindingMode.Default;

Defensive patterns

Strategy: validation

Validate before calling

if (!Enum.IsDefined(typeof(BindingMode), value))
    throw new InvalidEnumArgumentException(nameof(value), (int)value, typeof(BindingMode));
binding.Mode = (BindingMode)value;

Type guard

static bool IsValidBindingMode(int v) => Enum.IsDefined(typeof(BindingMode), v);

Try / catch

try { binding.Mode = (BindingMode)stored; } catch (InvalidEnumArgumentException) { binding.Mode = BindingMode.Default; }

Prevention

Never cast raw ints to enums without Enum.IsDefined.
Normalize persisted enum values at deserialization time.
Prefer BindingMode.Default when the stored value is unknown.

When it happens

Trigger: binding.Mode = (BindingMode)99; enum values from deserialized config/data that exceed the BindingMode range; corrupted stored enum values assigned in code.

Common situations: Persisting enum values in settings files and casting them back unchecked; interop code receiving ints from external systems; generic data-binding frameworks assigning raw ints.

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/21ed1734d5073d7f. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Data/Binding.cs:363

            {
                switch (GetFlagsWithinMask(BindingFlags.PropagationMask))
                {
                    case BindingFlags.OneWay:           return BindingMode.OneWay;
                    case BindingFlags.TwoWay:           return BindingMode.TwoWay;
                    case BindingFlags.OneWayToSource:   return BindingMode.OneWayToSource;
                    case BindingFlags.OneTime:          return BindingMode.OneTime;
                    case BindingFlags.PropDefault:      return BindingMode.Default;
                }
                Invariant.Assert(false, "Unexpected BindingMode value");
                return 0;
            }
            set
            {
                CheckSealed();

                BindingFlags flags = FlagsFrom(value);
                if (flags == BindingFlags.IllegalInput)
                    throw new InvalidEnumArgumentException("value", (int) value, typeof(BindingMode));

                ChangeFlagsWithinMask(BindingFlags.PropagationMask, flags);
            }
        }

        /// <summary> Update type </summary>
        [DefaultValue(UpdateSourceTrigger.Default)]
        public UpdateSourceTrigger UpdateSourceTrigger
        {
            get
            {
                switch (GetFlagsWithinMask(BindingFlags.UpdateMask))
                {
                    case BindingFlags.UpdateOnPropertyChanged: return UpdateSourceTrigger.PropertyChanged;
                    case BindingFlags.UpdateOnLostFocus:    return UpdateSourceTrigger.LostFocus;
                    case BindingFlags.UpdateExplicitly:     return UpdateSourceTrigger.Explicit;
                    case BindingFlags.UpdateDefault:        return UpdateSourceTrigger.Default;
                }

View on GitHub (pinned to 81131a70a4)