dotnet/wpf · error · FileFormatException

SR.InvalidSFContentType

Error message

SR.InvalidSFContentType

What it means

FixedDocument.GetStoryFragments throws FileFormatException with SR.InvalidSFContentType when the StoryFragments part referenced by the package has a MIME content type that does not match the required StoryFragments type. Like the DocumentStructure check, the part is loaded and its ContentType compared type-and-subtype against the expected value; any mismatch aborts the load as a file format error.

Solutions

  1. Regenerate the XPS so the StoryFragments part carries the required MIME type.
  2. Correct the [Content_Types].xml Override for the StoryFragments part to the proper story-fragments content type.
  3. If story structure is not needed, remove the StoryFragments relationship/part entirely so it is not loaded with a bad type.

Example fix

// before ([Content_Types].xml in package)
<Default Extension="xml" ContentType="application/xml" />

// after
<Override PartName="/Documents/1/StoryFragments.xml" ContentType="application/vnd.ms-package.story-fragments+xml" />
Defensive patterns

Strategy: try-catch

Validate before calling

// pre-validate the package part before loading
// confirm the StoryFragments part's Content-Type in [Content_Types].xml
// matches the required story-fragments MIME type.

Try / catch

try
{
    var fragments = fixedDocument.GetStoryFragments();
}
catch (FileFormatException ex)
{
    logger.LogError(ex, "XPS package has an invalid StoryFragments content type.");
}

Prevention

When it happens

Trigger: Loading an XPS FixedDocument whose StoryFragments part (accessibility/story metadata) declares an incorrect Content-Type in [Content_Types].xml, or whose part was created/written by a generator that labeled it with a generic XML type.

Common situations: Third-party XPS producers omitting or mistyping the StoryFragments Override entry; repackaging tools rewriting content types incorrectly; documents edited by hand.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/29878f41d137151e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/FixedDocument.cs:910

            object o = null;

            Uri baseUri = BaseUriHelper.GetBaseUri(fixedPage);

            if (baseUri.Scheme.Equals(PackUriHelper.UriSchemePack, StringComparison.OrdinalIgnoreCase))
            {
                // avoid the case of pack://application,,,
                if (!baseUri.Host.Equals(BaseUriHelper.PackAppBaseUri.Host) &&
                    !baseUri.Host.Equals(BaseUriHelper.SiteOfOriginBaseUri.Host))
                {
                    Uri structureUri = GetStructureUriFromRelationship(baseUri, _storyFragmentsRelationshipName);

                    if (structureUri != null)
                    {
                        ContentType mimeType;
                        o = ValidateAndLoadPartFromAbsoluteUri(structureUri, false, null, out mimeType);
                        if (!_storyFragmentsContentType.AreTypeAndSubTypeEqual(mimeType))
                        {
                            throw new FileFormatException(SR.InvalidSFContentType);
                        }
                        if (!(o is StoryFragments))
                        {
                            throw new FileFormatException(SR.InvalidStoryFragmentsMarkup);
                        }
                    }
                }
            }

            return o as StoryFragments;
        }


        private static object ValidateAndLoadPartFromAbsoluteUri(Uri AbsoluteUriDoc, bool validateOnly, string rootElement, out ContentType mimeType)
        {
            mimeType = null;
            Stream pageStream = null;
            object o = null;

View on GitHub (pinned to 81131a70a4)