What causes "CultureSource" in dotnet/wpf?

Assign only named enum members: NumberCultureSource.User, .Text, or .Override

dotnet/wpf · error · InvalidEnumArgumentException

CultureSource

Error message

CultureSource

What it means

NumberSubstitution.CultureSource setter validates the value against the NumberCultureSource enum range ((uint)value > NumberCultureSource.Override) and throws InvalidEnumArgumentException("CultureSource", ...). Only User (0), Text (1), Override (2) are accepted.

Solutions

Assign only named enum members: NumberCultureSource.User, .Text, or .Override
Validate/normalize any integer before casting: if (!Enum.IsDefined(typeof(NumberCultureSource), v)) throw/fallback
Clamp values read from external config to the valid range 0..2
Fix the data source (XAML resource or settings file) that contains the out-of-range value

Example fix

// before
numberSubstitution.CultureSource = (NumberCultureSource)intValue; // intValue = 7
// after
if (Enum.IsDefined(typeof(NumberCultureSource), intValue))
    numberSubstitution.CultureSource = (NumberCultureSource)intValue;
else
    numberSubstitution.CultureSource = NumberCultureSource.AsCulture;

Defensive patterns

Strategy: validation

Validate before calling

if (!Enum.IsDefined(typeof(NumberCultureSource), value)) value = NumberCultureSource.AsCulture;

Type guard

bool IsValidCultureSource(int v) => v >= 0 && v <= (int)NumberCultureSource.Override;

Try / catch

try { numberSubstitution.CultureSource = source; }
catch (InvalidEnumArgumentException ex) { log.Warn("Invalid CultureSource, using default", ex); numberSubstitution.CultureSource = NumberCultureSource.AsCulture; }

Prevention

Only assign named enum members
Validate serialized/config integers with Enum.IsDefined before casting
Clamp UI-bound integer values to the enum range

When it happens

Trigger: Assigning NumberSubstitution.CultureSource a value not defined in NumberCultureSource — an invalid cast like (NumberCultureSource)7, an uninitialized/out-of-range value read from config or serialized data.

Common situations: Deserializing NumberSubstitution settings from XAML/app config with an out-of-range integer; arithmetic on enum values; binding a UI control's integer value directly to the property without clamping.

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/e1452c2134135070. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/textformatting/NumberSubstitution.cs:54

        {
            _source = source;
            _cultureOverride = ThrowIfInvalidCultureOverride(cultureOverride);
            _substitution = substitution;
        }

        /// <summary>
        /// The CultureSource property specifies how the culture for numbers
        /// is determined. The default value is NumberCultureSource.Text,
        /// which means the number culture is the culture of the text run.
        /// </summary>
        public NumberCultureSource CultureSource
        {
            get { return _source; }

            set
            {
                if ((uint)value > (uint)NumberCultureSource.Override)
                    throw new InvalidEnumArgumentException("CultureSource", (int)value, typeof(NumberCultureSource));

                _source = value;
            }
        }

        /// <summary>
        /// If the CultureSource == NumberCultureSource.Override, this 
        /// property specifies the number culture. A value of null is interpreted 
        /// as US-English. The default value is null. If CultureSource != 
        /// NumberCultureSource.Override, this property is ignored.
        /// </summary>
        [TypeConverter(typeof(System.Windows.CultureInfoIetfLanguageTagConverter))]
        public CultureInfo CultureOverride
        {
            get { return _cultureOverride; }
            set { _cultureOverride = ThrowIfInvalidCultureOverride(value); }
        }

View on GitHub (pinned to 81131a70a4)