stride3d/stride · error · ArgumentException

The parameter of this converter must be an instance of the…

Error message

The parameter of this converter must be an instance of the Size structure. Use {sd:Size (arguments)} to construct one.

What it means

NumericToSize requires its ConverterParameter to be a WPF System.Windows.Size instance, which the converter scales by the numeric bound value. If the parameter is missing, is a string, or is any other type, this ArgumentException is thrown. The message points to the {sd:Size (arguments)} markup extension as the intended way to construct the parameter in XAML.

Solutions

Declare the parameter with the sd:Size markup extension, e.g. ConverterParameter="{sd:Size 100, 50}"
Or bind a Size resource/static value as ConverterParameter
Verify you did not confuse NumericToSize with a converter that takes string parameters
If the string form is unavoidable, wrap in a markup extension or convert to Size before binding

Example fix

// before
Converter="{sd:NumericToSize}" ConverterParameter="100,50"
// after
Converter="{sd:NumericToSize}" ConverterParameter="{sd:Size 100, 50}"

Defensive patterns

Strategy: type-guard

Validate before calling

bool IsValidSizeParameter(object parameter) => parameter is System.Windows.Size;

Type guard

bool IsSize(object p) => p is System.Windows.Size size && !double.IsNaN(size.Width) && !double.IsNaN(size.Height);

Try / catch

try
{
    return converter.Convert(value, typeof(Size), parameter, culture);
}
catch (ArgumentException)
{
    return new Size(0, 0);
}

Prevention

Always construct the parameter with ConverterParameter="{sd:Size w, h}"
Never pass raw strings like "100,50" as ConverterParameter for this converter
Check parameter type at binding authoring time with a debug converter or trace output
Prefer a Size resource (StaticResource) over string parameters

When it happens

Trigger: Using ConverterParameter="100,50" (a string) instead of a Size instance; omitting ConverterParameter entirely (parameter is null); passing a numeric or Thickness parameter by mistake to NumericToSize.

Common situations: Copy-pasting a converter usage from NumericToThickness and leaving a string parameter; authors unfamiliar with markup extensions passing raw XAML strings as parameters; tooling that only supports primitive ConverterParameter values.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/b11b0c32e6adbc85. Report an issue: GitHub.

Appendix: source

Thrown at sources/presentation/Stride.Core.Presentation.Wpf/ValueConverters/NumericToSize.cs:36

    public class NumericToSize : ValueConverterBase<NumericToSize>
    {
        /// <inheritdoc/>
        [NotNull]
        public override object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            double scalar;
            try
            {
                scalar = ConverterHelper.ConvertToDouble(value, culture);
            }
            catch (Exception exception)
            {
                throw new ArgumentException("The value of this converter must be convertible to a double.", exception);
            }

            if (!(parameter is Size))
            {
                throw new ArgumentException("The parameter of this converter must be an instance of the Size structure. Use {sd:Size (arguments)} to construct one.");
            }

            var size = (Size)parameter;
            var result = new Size(size.Width * scalar, size.Height * scalar);
            return result;
        }

        /// <inheritdoc/>
        public override object ConvertBack(object value, [NotNull] Type targetType, object parameter, CultureInfo culture)
        {
            if (!(value is Size))
            {
                throw new ArgumentException("The value of the ConvertBack method of this converter must be a an instance of the Size structure.");
            }
            if (!(parameter is Size))
            {
                throw new ArgumentException("The parameter of the ConvertBack method of this converter must be a an instance of the Size structure.");
            }

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