dotnet/wpf · error · XmlException

SR.Format(SR.RequiredAttributeMissing…

Error message

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

What it means

XmlException from Annotation.ReadAttributes (reached via ReadXml when deserializing annotation XML): the required CreationTime attribute is absent from the Annotation element, so the annotation markup is malformed and cannot be deserialized.

Solutions

Add the CreationTime attribute with a valid xsd:dateTime value (e.g. '2026-09-14T10:00:00').
Regenerate the annotation file from the creating application.
Check the attribute spelling is exactly 'CreationTime'.
Pre-validate required attributes before calling ReadXml.

Example fix

// before
<Annotation Id="..." TypeName="Highlight" LastModificationTime="...">
// after
<Annotation Id="..." TypeName="Highlight" CreationTime="2026-09-14T10:00:00" LastModificationTime="...">

Defensive patterns

Strategy: validation

Validate before calling

bool HasCreationTime(XElement el) => DateTime.TryParse(el.Attribute("CreationTime")?.Value, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out _);

Try / catch

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

Prevention

Always emit CreationTime in xsd:dateTime round-trip format with invariant culture.
Do not strip 'optional-looking' attributes during XML preprocessing.
Schema-validate the annotation stream before load.

When it happens

Trigger: Loading annotation XML whose <Annotation> element lacks the CreationTime attribute, e.g. after stripping attributes or when the file was produced by tooling that omitted it.

Common situations: Hand-constructed annotation files, minified or sanitized XML, or copy/paste of annotation elements without all required attributes.

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/48b8e1473e9b61c5. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Annotations/Annotation.cs:676

                            throw new FormatException(SR.Format(SR.InvalidAttributeValue, AnnotationXmlConstants.Attributes.TypeName));
                        }
                        break;

                    default:
                        if (!Annotation.IsNamespaceDeclaration(reader))
                           throw new XmlException(SR.Format(SR.UnexpectedAttribute, reader.LocalName, AnnotationXmlConstants.Elements.Annotation));
                       break;
                }
            }

            // 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);
        }

View on GitHub (pinned to 81131a70a4)