dotnet/wpf · error · XmlException

SR.Format(SR.RequiredAttributeMissing…

Error message

SR.Format(SR.RequiredAttributeMissing, AnnotationXmlConstants.Attributes.TypeName, AnnotationXmlConstants.Elements.Annotation)

What it means

ReadAttributes requires the TypeName attribute identifying the annotation type (e.g. Highlight, TextStickyNote). If _typeName is still null after attribute parsing, an XmlException is thrown because the type drives how the annotation is instantiated.

Solutions

Add TypeName with a valid annotation type value (e.g. 'Highlight', 'TextStickyNote', 'InkStickyNote').
Ensure the spelling matches AnnotationXmlConstants.Attributes.TypeName so it is recognized rather than rejected as unexpected.
Regenerate the annotation stream via AnnotationStore/AnnotationService.
Validate required attributes (Id, TypeName, CreationTime, LastModificationTime) before load.

Example fix

// before
<Annotation Id="..." CreationTime="..." LastModificationTime="...">
// after
<Annotation Id="..." TypeName="Highlight" CreationTime="..." LastModificationTime="...">

Defensive patterns

Strategy: validation

Validate before calling

bool HasTypeName(XElement el) => !string.IsNullOrEmpty(el.Attribute("TypeName")?.Value) && new[]{"Highlight","TextStickyNote","InkStickyNote"}.Contains(el.Attribute("TypeName").Value);

Try / catch

try { annotationStore.Load(stream); } catch (XmlException ex) { log.Error("Missing annotation TypeName: " + ex.Message); }

Prevention

Always include a known TypeName value when producing annotation XML.
Check for misspelled attribute names that end up rejected as unexpected before the missing-attribute error fires.
Use AnnotationService/AnnotationStore to author annotation XML.

When it happens

Trigger: Loading annotation XML whose <Annotation> element lacks the TypeName attribute, or where TypeName was misspelled so it was rejected earlier as an unexpected attribute.

Common situations: Custom annotation producers that omit TypeName, hand-written XML, or attribute renamed by a transformation step.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/cdcca03e5d8a318e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Annotations/Annotation.cs:684

                }
            }

            // Test to see if any required attribute was missing
            if (_id.Equals(Guid.Empty))
            {
                throw new XmlException(SR.Format(SR.RequiredAttributeMissing, AnnotationXmlConstants.Attributes.Id, AnnotationXmlConstants.Elements.Annotation));
            }
            if (_created.Equals(DateTime.MinValue))
            {
                throw new XmlException(SR.Format(SR.RequiredAttributeMissing, AnnotationXmlConstants.Attributes.CreationTime, AnnotationXmlConstants.Elements.Annotation));
            }
            if (_modified.Equals(DateTime.MinValue))
            {
                throw new XmlException(SR.Format(SR.RequiredAttributeMissing, AnnotationXmlConstants.Attributes.LastModificationTime, AnnotationXmlConstants.Elements.Annotation));
            }
            if (_typeName == null)
            {
                throw new XmlException(SR.Format(SR.RequiredAttributeMissing, AnnotationXmlConstants.Attributes.TypeName, AnnotationXmlConstants.Elements.Annotation));
            }

            // Move back to the parent "Annotation" element
            reader.MoveToContent();
        }

        private void OnCargoChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
        {
            FireResourceEvent((AnnotationResource)sender, AnnotationAction.Modified, CargoChanged);
        }

        private void OnCargosChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            AnnotationAction action = AnnotationAction.Added;
            IList changedItems = null;

            switch (e.Action)
            {

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