dotnet/wpf · error · ArgumentException

SR.TypeNameMustBeSpecified

Error message

SR.TypeNameMustBeSpecified

What it means

ContentLocatorPart's constructor requires an XmlQualifiedName whose Name is non-empty. WPF Annotations throws ArgumentException(SR.TypeNameMustBeSpecified) when partType.Name is null or the empty string, because a locator part is meaningless without a type name. The parameter name reported in the exception is "partType.Name".

Solutions

  1. Ensure the XmlQualifiedName passed to the constructor has a non-empty Name property.
  2. Validate the name before constructing the ContentLocatorPart and surface a domain-specific error.
  3. If the name can legitimately be absent, do not create a ContentLocatorPart; model that case explicitly.

Example fix

// before
var qname = new XmlQualifiedName();
var part = new ContentLocatorPart(qname); // throws
// after
if (string.IsNullOrEmpty(qname.Name)) throw new InvalidOperationException("Locator part type name is required");
var part = new ContentLocatorPart(new XmlQualifiedName("MyPartType", qname.Namespace));
Defensive patterns

Strategy: validation

Validate before calling

if (partType == null || string.IsNullOrEmpty(partType.Name))
    throw new ArgumentException("A non-empty type name is required.", nameof(partType));

Type guard

static bool IsValidLocatorPartType(XmlQualifiedName q) => q != null && !string.IsNullOrEmpty(q.Name);

Try / catch

try { var part = new ContentLocatorPart(partType); }
catch (ArgumentException ex) when (ex.ParamName == "partType.Name") { /* fall back to a default part type or report */ }

Prevention

When it happens

Trigger: new ContentLocatorPart(new XmlQualifiedName("")) or new ContentLocatorPart(new XmlQualifiedName(null, "ns")) - the qualified name's Name property is null or empty.

Common situations: Building locator parts dynamically from deserialized or user-supplied XML where the local name was lost; constructing XmlQualifiedName via its parameterless default constructor and forgetting to set Name; mapping from external schemas where the element name is optional.

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

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/53385f5cd0316339. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Annotations/LocatorPart.cs:48

        //
        //  Constructors
        //
        //------------------------------------------------------

        #region Constructors

        /// <summary>
        ///     Creates a ContentLocatorPart with the specified type name and namespace.
        /// </summary>
        /// <param name="partType">fully qualified locator part's type</param>
        /// <exception cref="ArgumentNullException">partType is null</exception>
        /// <exception cref="ArgumentException">partType.Namespace or partType.Name is null or empty string</exception>
        public ContentLocatorPart(XmlQualifiedName partType)
        {
            ArgumentNullException.ThrowIfNull(partType);
            if (String.IsNullOrEmpty(partType.Name))
            {
                throw new ArgumentException(SR.TypeNameMustBeSpecified, "partType.Name");
            }
            if (String.IsNullOrEmpty(partType.Namespace))
            {
                throw new ArgumentException(SR.TypeNameMustBeSpecified, "partType.Namespace");
            }

            _type = partType;
            _nameValues = new ObservableDictionary();
            _nameValues.PropertyChanged += OnPropertyChanged;
        }

        #endregion Constructors

        //------------------------------------------------------
        //
        //  Public Methods
        //
        //------------------------------------------------------

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