dotnet/wpf · error · XamlUnexpectedParseException

Element ::= . EmptyElement | ( StartElement ElementBody ).

Error message

Element ::= . EmptyElement | ( StartElement ElementBody ).

What it means

XamlPullParser.P_Element implements the grammar rule `Element ::= EmptyElement | (StartElement ElementBody)`. When the current scanner node is neither an EMPTYELEMENT nor an ELEMENT token, it throws XamlUnexpectedParseException with the Element rule text. The pull parser is driven by a scanner; this is a grammar-invariant check that a new element parse actually begins at an element node.

Solutions

  1. Ensure the XAML source is well-formed XML (validate with an XML parser) before Load.
  2. Check for stray or duplicated end tags / text nodes where an element should start.
  3. If using a custom scanner or reader, verify it emits EMPTYELEMENT/ELEMENT nodes where P_Element is invoked.
  4. Isolate the failing fragment by loading the document progressively and catching XamlUnexpectedParseException to find the offset.

Example fix

<!-- before -->
<Grid>
  </Button>
</Grid>

<!-- after -->
<Grid>
  <Button />
</Grid>
Defensive patterns

Strategy: try-catch

Validate before calling

// Validate well-formedness before Load
var doc = new System.Xml.XmlDocument();
doc.LoadXml(xaml); // throws XmlException if not well-formed

Try / catch

try { return XamlReader.Parse(xaml); } catch (XamlUnexpectedParseException ex) { Log($"Unexpected node {ex.NodeType} where element expected"); return null; }

Prevention

When it happens

Trigger: Invoking the parser pipeline (Parse / P_ElementContent / P_PropertyContent paths) on scanner output where the current node is e.g. ENDTAG, TEXT, or a directive when an element start is expected — typically from malformed or non-well-formed XML fed to XamlXmlReader/XamlReader.Load.

Common situations: Feeding truncated XAML streams to XamlReader.Load; custom XamlReader/scanner implementations emitting node sequences out of grammar order; documents with stray closing tags or text where an element is required.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/fca1046158f4f2ed. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Parser/XamlPullParser.cs:114

                    yield return node;
                }

                break;

            case ScannerNodeType.ELEMENT:
                foreach (XamlNode node in P_StartElement())
                {
                    yield return node;
                }

                foreach (XamlNode node in P_ElementBody())
                {
                    yield return node;
                }

                break;
            default:
                throw new XamlUnexpectedParseException(_xamlScanner, nodeType, ElementRuleException);
            }
        }

        ///////////////////////////
        //  EmptyElement ::= EMPTYELEMENT DIRECTIVE* ATTRIBUTE*
        //
        public IEnumerable<XamlNode> P_EmptyElement()
        {
            if (_xamlScanner.NodeType != ScannerNodeType.EMPTYELEMENT)
            {
                throw new XamlUnexpectedParseException(_xamlScanner, _xamlScanner.NodeType,
                    EmptyElementRuleException);
            }

            yield return Logic_StartObject(_xamlScanner.Type, _xamlScanner.Namespace);
            _xamlScanner.Read();
            if (ProvideLineInfo)
            {

View on GitHub (pinned to 81131a70a4)