dotnet/wpf · error · InvalidOperationException

SR.MissingNameProvider

Error message

SR.MissingNameProvider

What it means

NameReferenceConverter.ConvertTo throws InvalidOperationException (SR.MissingNameProvider) when the context's GetService(typeof(IXamlNameProvider)) returns null. Serializing an object back to its XAML name requires an IXamlNameProvider service; without it the converter cannot produce a name string. This mirrors the ConvertFrom MissingNameResolver error on the serialization side.

Solutions

  1. Invoke ConvertTo within a XAML serialization pipeline (XamlObjectWriter/XamlXmlWriter ecosystem) that provides IXamlNameProvider.
  2. In custom hosts, implement and register IXamlNameProvider on the service provider backing the context.
  3. Check for the service's availability before calling ConvertTo and choose a fallback serialization strategy otherwise.

Example fix

// before
converter.ConvertTo(new PlainContext(), culture, obj, typeof(string)); // no IXamlNameProvider
// after
var ctx = new XamlSerializationContext(serviceProviderWithNameProvider);
var name = (string)converter.ConvertTo(ctx, culture, obj, typeof(string));
Defensive patterns

Strategy: type-guard

Validate before calling

var nameProvider = context?.GetService(typeof(IXamlNameProvider));
if (nameProvider is null) throw new InvalidOperationException("IXamlNameProvider service unavailable; cannot serialize name");

Type guard

bool CanConvertToName(ITypeDescriptorContext ctx) => ctx?.GetService(typeof(IXamlNameProvider)) is IXamlNameProvider;

Try / catch

try { var name = (string)converter.ConvertTo(context, culture, obj, typeof(string)); }
catch (InvalidOperationException ex) when (ex.Message == SR.MissingNameProvider) { /* use fallback serialization */ }

Prevention

When it happens

Trigger: Calling ConvertTo with an ITypeDescriptorContext whose GetService(typeof(IXamlNameProvider)) returns null — e.g. serializing outside a XAML save pipeline or with a stub context.

Common situations: Custom XAML serializers or designer export paths that forget to supply IXamlNameProvider; unit tests exercising ConvertTo with minimal contexts; serialization invoked before the name scope has been established.

Understand the failure class

Background: "not installed", "pip install", "required for": how missing-dependency errors surface across open-source libraries — this error's family across 34 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/e5ab04cf30d71a97. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Windows/Markup/NameReferenceConverter.cs:72

                return false;
            }

            if (destinationType == typeof(string))
            {
                return true;
            }

            return base.CanConvertTo(context, destinationType);
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            ArgumentNullException.ThrowIfNull(context);

            var nameProvider = (IXamlNameProvider)context.GetService(typeof(IXamlNameProvider));
            if (nameProvider is null)
            {
                throw new InvalidOperationException(SR.MissingNameProvider);
            }

            return nameProvider.GetName(value);
        }
    }
}

View on GitHub (pinned to 81131a70a4)