dotnet/wpf · error · NotSupportedException

Cannot convert from type.

Error message

Cannot convert from type.

What it means

ImageSourceTypeConverter.ConvertFrom is not implemented: after validating that the value is a supported source type, it throws NotImplementedException. Converting any object (e.g. a string URI or stream) into a BitmapSource via this converter is unsupported by design — use BitmapFrame/Create APIs instead.

Solutions

1. Do not use ImageSourceTypeConverter for value creation; construct the image with BitmapFrame.Create(uri) or new BitmapImage(new Uri(path)).
2. If invoked indirectly by a framework, register a different TypeConverter that implements ConvertFrom.
3. Catch NotImplementedException and perform the conversion manually via BitmapFrame.Create.

Example fix

// before
var source = (BitmapSource)converter.ConvertFrom(context, culture, imagePath);

// after
var source = (BitmapSource)BitmapFrame.Create(new Uri(imagePath));

try
{
    source = (BitmapSource)converter.ConvertFrom(context, culture, value);
}
catch (NotImplementedException)
{
    source = BitmapFrame.Create((Uri)value); // manual construction
}

When it happens

Trigger: Calling ImageSourceTypeConverter.ConvertFrom(context, culture, value) with any supported type value; TypeConverter.ConvertFromString / ConvertFrom invoked by parsers or designers on an image-source property handled by this converter.

Common situations: XAML or designer pipelines attempting to convert an image path string via this converter; developers using TypeDescriptor to build BitmapSource values during XPS serialization setup.

Related errors

• The method or operation is not implemented.
• Cannot convert to type.
• The method or operation is not implemented.
• 'value' must be of type 'BitmapSource'.
• " }} " element found. Expected fixed page element ( }} ).

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/85507071683a6b69. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/ReachFramework/Serialization/ImageSourceTypeConverter.cs:112

        /// The Object to convert.
        /// </param>
        /// <returns>
        /// An Object that represents the converted value.
        /// </returns>
        public
        override
        object
        ConvertFrom(
            ITypeDescriptorContext              context,
            System.Globalization.CultureInfo    culture,
            object                              value
            )
        {
            ArgumentNullException.ThrowIfNull(value);

            if (!IsSupportedType(value.GetType()))
            {
                throw new NotSupportedException(SR.Converter_ConvertFromNotSupported);
            }

            throw new NotImplementedException();
        }

        /// <summary>
        /// Converts the given value object to the specified type,
        /// using the arguments.
        /// </summary>
        /// <param name="context">
        /// An ITypeDescriptorContext that provides a format context.
        /// </param>
        /// <param name="culture">
        /// A CultureInfo object. If null is passed, the current
        /// culture is assumed.
        /// </param>
        /// <param name="value">
        /// The Object to convert.

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