dotnet/wpf · error · XamlUnexpectedParseException

EmptyPropertyElement ::= EMPTYPROPERTYELEMENT.

Error message

EmptyPropertyElement ::= EMPTYPROPERTYELEMENT.

What it means

P_EmptyPropertyElement implements EmptyPropertyElement ::= EMPTYPROPERTYELEMENT. It throws XamlUnexpectedParseException if the scanner's current node is not an EMPTYPROPERTYELEMENT, i.e. the parser expected a self-closing property element but found a different node kind. The library throws this to enforce that this production is only invoked at the correct scanner state.

Solutions

Correct the markup so the empty property element is truly self-closing (e.g. <Grid.RowDefinitions/>) at the reported position
Re-run the scanner from a clean stream; do not reuse a partially consumed XamlXmlReader
Verify no custom node-stream injection (XamlNodeList rewinding) is desynchronizing NodeType

Example fix

// before
<Grid.RowDefinitions>
</Grid.RowDefinitions>
// after (or a fully-formed nonempty element)
<Grid.RowDefinitions>
  <RowDefinition Height="Auto" />
</Grid.RowDefinitions>

Defensive patterns

Strategy: validation

Validate before calling

if (!xaml.TrimEnd().EndsWith("/>")) throw new InvalidOperationException("Expected self-closing property element");

Try / catch

try { reader.Read(); /* node loop */ } catch (System.Xaml.XamlParseException ex) { HandleParseFailure(ex.LineNumber, ex.LinePosition, ex.Message); }

Prevention

Write empty property elements as <Owner.Property/> when they have no content
Verify scanner state only advances through the public XamlXmlReader API
Round-trip markup through XamlXmlWriter to normalize node forms

When it happens

Trigger: Internal parser dispatch reaches P_EmptyPropertyElement (via P_PropertyElement) while _xamlScanner.NodeType != ScannerNodeType.EMPTYPROPERTYELEMENT — a parser/scanner desynchronization caused by malformed or non-canonical markup.

Common situations: Malformed XAML where a property element position contains a non-empty element or other token; custom IXamlXmlParser pipelines feeding nodes out of order; bugs in third-party markup that mimics property elements.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/92cbcb110528a4c4. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Parser/XamlPullParser.cs:351

                    {
                        yield return node;
                    }

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

        ///////////////////////////
        //  EmptyPropertyElement ::= EMPTYPROPERTYELEMENT
        //
        public IEnumerable<XamlNode> P_EmptyPropertyElement()
        {
            if (_xamlScanner.NodeType != ScannerNodeType.EMPTYPROPERTYELEMENT)
            {
                throw new XamlUnexpectedParseException(_xamlScanner, _xamlScanner.NodeType,
                    EmptyPropertyElementRuleException);
            }

            yield return Logic_StartMember(_xamlScanner.PropertyElement);
            yield return Logic_EndMember();
            _xamlScanner.Read();
            if (ProvideLineInfo)
            {
                yield return Logic_LineInfo();
            }
        }

        ///////////////////////////
        //  NonemptyPropertyElement ::= PROPERTYELEMENT PropertyContent* ENDTAG
        //
        public IEnumerable<XamlNode> P_NonemptyPropertyElement()
        {
            if (_xamlScanner.NodeType != ScannerNodeType.PROPERTYELEMENT)

View on GitHub (pinned to 81131a70a4)