dotnet/wpf · error · InvalidOperationException

SR.MustHaveName

Error message

SR.MustHaveName

What it means

ReferenceExtension.ProvideValue throws InvalidOperationException (SR.MustHaveName) when the extension's Name property is null or empty. {x:Reference} requires a non-empty name to pass to IXamlNameResolver.Resolve. The check runs after the name-resolver service is obtained, before any lookup.

Solutions

1. Set Name (or use the ReferenceExtension(string) constructor) with a non-empty value before ProvideValue.
2. In XAML, always supply the Name attribute on x:Reference elements.
3. Guard dynamic scenarios: skip creating the extension when the source name is empty.

Example fix

// before
var ext = new ReferenceExtension();
var v = ext.ProvideValue(provider); // throws: Name is null
// after
var ext = new ReferenceExtension("btnOk");
var v = ext.ProvideValue(provider);

if (string.IsNullOrEmpty(ext.Name))
    throw new InvalidOperationException("ReferenceExtension.Name must be a non-empty string before ProvideValue");

bool IsUsableReference(ReferenceExtension ext) => ext is not null && !string.IsNullOrEmpty(ext.Name);

try { var v = ext.ProvideValue(provider); }
catch (InvalidOperationException) { /* Name unset — supply or skip the reference */ }

When it happens

Trigger: Creating a ReferenceExtension via the parameterless constructor (or with Name = null/"") and calling ProvideValue without setting Name.

Common situations: XAML with <x:Reference> missing the Name attribute; dynamic construction of the extension where the name binding resolved to an empty string; template/generated XAML with unfilled placeholders.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• InvalidOperationException(SR.XamlTypeNameNameIsNullOrEmpty)
• SR.MissingNameResolver
• SR.MustHaveName
• ' '.' ' is a property without a getter and is not a valid…
• ' '.' ' is a property without a getter and is not a valid…

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/03fceae26f598d57. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Windows/Markup/Reference.cs:35

        public Reference(string name)
        {
            Name = name;
        }

        [ConstructorArgument("name")]
        public string Name { get; set; }

        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            ArgumentNullException.ThrowIfNull(serviceProvider);
            if (serviceProvider.GetService(typeof(IXamlNameResolver)) is not IXamlNameResolver nameResolver)
            {
                throw new InvalidOperationException(SR.MissingNameResolver);
            }

            if (string.IsNullOrEmpty(Name))
            {
                throw new InvalidOperationException(SR.MustHaveName);
            }

            object obj = nameResolver.Resolve(Name);
            if (obj is null)
            {
                string[] names = new string[] { Name };
                obj = nameResolver.GetFixupToken(names, true);
            }

            return obj;
        }
    }
}

View on GitHub (pinned to 81131a70a4)