dotnet/wpf · error · ArgumentException

SR.ParserAttributeArgsHigh with…

Error message

SR.ParserAttributeArgsHigh with 'XmlnsCompatibleWithAttribute' (too many constructor arguments for XmlnsCompatibleWithAttribute)

What it means

In XmlnsCache, GetNamespacesFromCompatAttr parses an [XmlnsCompatibleWithAttribute] constructor arguments (oldNamespace, newNamespace). If the attribute carries more than two arguments, an ArgumentException with ParserAttributeArgsHigh is thrown because WPF only supports the two-argument constructor.

Solutions

  1. Use exactly the two-argument constructor: (oldNamespace, newNamespace)
  2. Remove any extra arguments or express them as named properties if the attribute type allows
  3. Verify the referenced attribute type is the standard System.Windows.Markup.XmlnsCompatibleWithAttribute

Example fix

// before
[assembly: XmlnsCompatibleWith("http://old/ns", "http://new/ns", "extraArg")]
// after
[assembly: XmlnsCompatibleWith("http://old/ns", "http://new/ns")]
Defensive patterns

Strategy: validation

Validate before calling

foreach (var attr in asm.GetCustomAttributesData())
{
    if (attr.AttributeType.Name == "XmlnsCompatibleWithAttribute" && attr.ConstructorArguments.Count != 2)
        throw new InvalidOperationException($"{asm}: XmlnsCompatibleWithAttribute must take exactly 2 arguments");
}

Try / catch

try { ProcessXmlnsCompatibleWithAttributes(asm); }
catch (ArgumentException ex) when (ex.Message.Contains("XmlnsCompatibleWithAttribute"))
{ log.Error("Malformed XmlnsCompatibleWithAttribute", ex); }

Prevention

When it happens

Trigger: An assembly declares [XmlnsCompatibleWith] with three or more constructor arguments and ProcessXmlnsCompatibleWithAttributes scans the assembly's custom attributes.

Common situations: Custom/extended XmlnsCompatibleWithAttribute with additional parameters; mismatched attribute definitions between assemblies; metadata-rewriting tools appending arguments.

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 dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/73c1f9ddefe1d191. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Markup/XmlnsCache.cs:265

        }

        private void GetNamespacesFromCompatAttr(CustomAttributeData data, out string oldXmlns, out string newXmlns)
        {
            // typedConstructorArguments (the Attribute constructor arguments)
            // [MyAttribute("test", Name=Hello)]
            // "test" is the Constructor Argument
            oldXmlns = null;
            newXmlns = null;
            IList<CustomAttributeTypedArgument> constructorArguments = data.ConstructorArguments;
            for (int i=0; i<constructorArguments.Count; i++)
            {
                CustomAttributeTypedArgument tca = constructorArguments[i];
                if (i == 0)
                    oldXmlns = tca.Value as String;
                else if (i == 1)
                    newXmlns = tca.Value as String;
                else
                    throw new ArgumentException(SR.Format(SR.ParserAttributeArgsHigh, "XmlnsCompatibleWithAttribute"));
            }
        }

#else

        private Attribute[] GetAttributes(Assembly asm, Type attrType)
        {
            return Attribute.GetCustomAttributes(asm, attrType);
        }

        private void GetNamespacesFromDefinitionAttr(Attribute attr, out string xmlns, out string clrns)
        {
            XmlnsDefinitionAttribute xmlnsAttr  = (XmlnsDefinitionAttribute)attr;
            xmlns = xmlnsAttr.XmlNamespace;
            clrns = xmlnsAttr.ClrNamespace;
        }

        private void GetNamespacesFromCompatAttr(Attribute attr, out string oldXmlns, out string newXmlns)

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