stride3d/stride · error · ArgumentException

The value of this converter must be convertible to a double.

Error message

The value of this converter must be convertible to a double.

What it means

NumericToSize multiplies a WPF Size structure (given as the converter parameter) by a numeric scalar (the bound value). The scalar is obtained via ConverterHelper.ConvertToDouble; when that conversion fails the library wraps the failure in this ArgumentException with the original exception as InnerException. It exists to fail fast when the bound value is not numeric rather than produce a degenerate Size.

Solutions

  1. Bind a numeric property (int/double) as the converter value
  2. Inspect InnerException to find the offending value
  3. Parse strings to numbers in the view model before binding
  4. Use CultureInfo-invariant parsing if strings come from user input

Example fix

// before
<Binding Path="WidthText"/> <!-- "12,5" string -->
// after
<Binding Path="Width"/> <!-- double 12.5 -->
Defensive patterns

Strategy: validation

Validate before calling

bool CanScaleToSize(object value) =>
    value is double || value is int || value is float || value is long || value is decimal ||
    (value is string s && double.TryParse(s, NumberStyles.Float, CultureInfo.InvariantCulture, out _));

Type guard

bool IsDoubleConvertible(object v) => v is double || v is int || v is float || v is long || v is decimal;

Try / catch

try
{
    return converter.Convert(value, typeof(Size), sizeParameter, culture);
}
catch (ArgumentException ex)
{
    Log(ex.InnerException);
    return (Size)sizeParameter; // unscaled fallback
}

Prevention

When it happens

Trigger: Convert(value, targetType, parameter, culture) is called with a value that ConverterHelper.ConvertToDouble cannot interpret: a non-numeric string like "auto", a Brush/Control instance, null, or a badly formatted localized number.

Common situations: Binding a string dimension (e.g. from a TextBox) instead of a numeric property; binding an object/enum to a Size-scaled element; culture-specific decimal separators breaking string-to-double conversion.

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/169c6550271814d9. Report an issue: GitHub.

Appendix: source

Thrown at sources/presentation/Stride.Core.Presentation.Wpf/ValueConverters/NumericToSize.cs:31

    /// A <see cref="Size"/> must be passed as a parameter of this converter. You can use the <see cref="MarkupExtensions.SizeExtension"/>
    /// markup extension to easily pass one, with the following syntax: {sd:Size (arguments)}. The resulting size will
    /// be the parameter size multiplied bu the scalar double value.
    /// </summary>
    [ValueConversion(typeof(double), typeof(Size))]
    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.");

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