dotnet/wpf · error · XpsPackagingException

FixedDocument has more than one related document structure.

Error message

FixedDocument has more than one related document structure.

What it means

XpsFixedDocumentReaderWriter.AddDocumentStructure throws XpsPackagingException (ReachPackaging_MoreThanOneDocStructure) when the FixedDocument already has a document structure part. The XPS spec permits at most one DocumentStructure relationship per FixedDocument. This is an eager check via the DocumentStructure property before creating a new structure part.

Solutions

Check the DocumentStructure property before calling AddDocumentStructure and skip if already non-null.
Track in application state whether the structure part was created for this document.
Rebuild the package if you truly need a new document structure; you cannot add a second one.

Example fix

// before
doc.AddDocumentStructure();
doc.AddDocumentStructure(); // throws
// after
if (doc.DocumentStructure == null)
    doc.AddDocumentStructure();

Defensive patterns

Strategy: validation

Validate before calling

if (doc.DocumentStructure == null)
    doc.AddDocumentStructure();

Try / catch

try { doc.AddDocumentStructure(); }
catch (XpsPackagingException) { /* structure already exists; reuse it */ }

Prevention

Guard every AddDocumentStructure call with a null check on DocumentStructure.
Make structure creation idempotent in helper methods.
Avoid retry wrappers that can re-run the creation step.

When it happens

Trigger: Calling AddDocumentStructure a second time on the same XpsFixedDocumentReaderWriter after a document structure part was already added (DocumentStructure property is non-null).

Common situations: Retry logic that re-invokes AddDocumentStructure after a partial failure; refactors that call it both in setup and in a write loop; accidental duplicate processing of the same document.

Understand the failure class

Background: "already exists" / EEXIST / FileAlreadyExistsException: what the 'file already exists' error means and how to fix it — this error's family across 37 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/f02951b8771b8661. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/ReachFramework/Packaging/XpsFixedDocumentReaderWriter.cs:475

            _thumbnail = CurrentXpsManager.AddThumbnail( imageType, this, Thumbnail );
            _metroPart.CreateRelationship( _thumbnail.Uri,
                                           TargetMode.Internal,
                                           XpsS0Markup.ThumbnailRelationshipName
                                          );
           return _thumbnail;
        }

        /// <summary>
        /// </summary>
        public
        XpsStructure
        AddDocumentStructure(
            )
        {
            if (this.DocumentStructure != null)
            {
                // Document structure already available for this FixedDocument
                throw new XpsPackagingException(SR.ReachPackaging_MoreThanOneDocStructure);
            }

            Uri pageUri = this.CurrentXpsManager.CreateStructureUri();
            //
            // Create the part and writer
            //
            PackagePart metroPart = this.CurrentXpsManager.GeneratePart(
                        XpsS0Markup.DocumentStructureContentType,
                        pageUri);

            _documentStructure = new XpsStructure(CurrentXpsManager, this, metroPart);

            //
            // Create the relationship between the document and the document-structure
            // Not in INode.Flush because IXpsFixedDocumentReader has no commit.
            //

            string structurePath = XpsManager.MakeRelativePath(this.Uri, _documentStructure.Uri);

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