dotnet/wpf · error · XmlException

SR.Format(SR.InvalidXmlContent…

Error message

SR.Format(SR.InvalidXmlContent, AnnotationXmlConstants.Elements.Item)

What it means

Item elements must be attribute-only; they may not contain child content. If an Item element is non-empty and the reader lands on anything other than the Item EndElement, ReadXml throws XmlException(SR.InvalidXmlContent, "Item").

Solutions

Remove all child nodes from Item elements; express all data via Name/Value attributes.
Regenerate the annotation stream with the standard WPF annotation writer.
Validate the XML structure before loading.

Example fix

// before
<Item Name="k" Value="v"><Extra>x</Extra></Item>
// after
<Item Name="k" Value="v"/>

Defensive patterns

Strategy: validation

Validate before calling

foreach (var item in doc.Descendants("Item"))
    if (!item.IsEmpty && item.Nodes().Any())
        throw new InvalidDataException("Item must not contain child content");

Try / catch

try { LoadAnnotations(stream); }
catch (XmlException ex) when (ex.Message.Contains("Item")) { /* strip Item children and retry, or reject the file */ }

Prevention

Treat Item as attribute-only; never nest elements or text inside it.
Sanitize externally produced annotation XML before loading.
Document the annotation XML contract for any tool that generates these files.

When it happens

Trigger: Deserializing annotations where an Item has children or inner text, e.g. <Item Name="k" Value="v"><Extra/></Item> or <Item Name="k" Value="v">text</Item>.

Common situations: Tools that serialize key/value pairs as nested elements; hand-edited annotation files; merging markup from other formats into annotation XML.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/252a6daeffaea594. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Annotations/LocatorPartList.cs:267

                                if (value == null)
                                {
                                    throw new XmlException(SR.Format(SR.RequiredAttributeMissing, AnnotationXmlConstants.Attributes.ItemValue, AnnotationXmlConstants.Elements.Item));
                                }

                                reader.MoveToContent();

                                part.NameValuePairs.Add(name, value);

                                bool isEmpty = reader.IsEmptyElement;

                                reader.Read();  // Read the beginning of the complete Item tag

                                if (!isEmpty)
                                {
                                    if (!(XmlNodeType.EndElement == reader.NodeType && AnnotationXmlConstants.Elements.Item == reader.LocalName))
                                    {
                                        // Should not contain any content, only attributes
                                        throw new XmlException(SR.Format(SR.InvalidXmlContent, AnnotationXmlConstants.Elements.Item));
                                    }
                                    else
                                    {
                                        reader.Read(); // Read the end of the Item tag
                                    }
                                }
                            }
                            else
                            {
                                // The locator part contains data other than just "Item" tags
                                throw new XmlException(SR.Format(SR.InvalidXmlContent, part.PartType.Name));
                            }
                        }
                    }

                    _parts.Add(part);

                    reader.Read();  // Read the ContentLocatorPart element

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