dotnet/wpf · error · ArgumentException

SR.Format(SR.InvalidCtorParameterUnknownFigureUnitType…

Error message

SR.Format(SR.InvalidCtorParameterUnknownFigureUnitType, "type")

What it means

The FigureLength constructor rejects a FigureUnitType outside the known set {Auto, Pixel, Column, Content, Page}, throwing ArgumentException with InvalidCtorParameterUnknownFigureUnitType. The unit type enum received a value not defined by FigureUnitType.

Solutions

Validate with Enum.IsDefined(typeof(FigureUnitType), type) before constructing.
Use only named FigureUnitType constants; avoid raw casts from int.
Fix the deserialization/config source producing the unknown value.

Example fix

// before
var unit = (FigureUnitType)rawInt;
var length = new FigureLength(value, unit); // throws on unknown unit

// after
var unit = (FigureUnitType)rawInt;
if (!Enum.IsDefined(typeof(FigureUnitType), unit))
    unit = FigureUnitType.Pixel;
var length = new FigureLength(value, unit);

Defensive patterns

Strategy: validation

Validate before calling

if (!Enum.IsDefined(typeof(FigureUnitType), type))
    throw new ArgumentException($"Unknown FigureUnitType: {type}");

Type guard

bool IsDefinedUnitType(FigureUnitType t) =>
    t is FigureUnitType.Auto or FigureUnitType.Pixel or FigureUnitType.Column
        or FigureUnitType.Content or FigureUnitType.Page;

Try / catch

try { var len = new FigureLength(value, type); }
catch (ArgumentException) { /* default to FigureUnitType.Pixel */ }

Prevention

Avoid raw int-to-enum casts; use named FigureUnitType constants.
Validate enum values from config/deserialization with Enum.IsDefined.
Watch for version-skew when enum values are persisted.

When it happens

Trigger: Calling new FigureLength(value, type) with an out-of-range or undefined FigureUnitType — e.g. an unvalidated cast from int or deserialization of a bad enum value.

Common situations: Casting raw ints to FigureUnitType from configuration or interop; enum values persisted by an older/newer version; deserializing corrupt or hand-edited XAML/serialized state.

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/8cdcf1dbf24d6677. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/FigureLength.cs:119

            if (double.IsNaN(value))
            {
                throw new ArgumentException(SR.Format(SR.InvalidCtorParameterNoNaN, "value"));
            }
            if (double.IsInfinity(value))
            {
                throw new ArgumentException(SR.Format(SR.InvalidCtorParameterNoInfinity, "value"));
            }
            if (value < 0.0)
            {
                throw new ArgumentOutOfRangeException(SR.Format(SR.InvalidCtorParameterNoNegative, "value"));
            }
            if (    type != FigureUnitType.Auto
                &&  type != FigureUnitType.Pixel
                &&  type != FigureUnitType.Column
                &&  type != FigureUnitType.Content
                &&  type != FigureUnitType.Page   )
            {
                throw new ArgumentException(SR.Format(SR.InvalidCtorParameterUnknownFigureUnitType, "type"));
            }
            if (type is FigureUnitType.Content or FigureUnitType.Page)
            {
                ArgumentOutOfRangeException.ThrowIfGreaterThan(value, 1.0);
            }

            if (type == FigureUnitType.Column)
            {
                ArgumentOutOfRangeException.ThrowIfGreaterThan(value, maxColumns);
            }

            if (type == FigureUnitType.Pixel)
            {
                ArgumentOutOfRangeException.ThrowIfGreaterThan(value, maxPixel);
            }

            _unitValue = (type == FigureUnitType.Auto) ? 0.0 : value;
            _unitType = type;

View on GitHub (pinned to 81131a70a4)