public void WriteExtraAttr() { string file = System.IO.Path.Combine(TestUtil.TestResultsDirectory, Guid.NewGuid().ToString() + ".docx"); CopyFileStream(TestFileStreams.HelloO14, file); //open it using the sdk using (var doc = WordprocessingDocument.Open(file, true)) { // Touch the font table part. var fontTablePart = doc.MainDocumentPart.GetPartsOfType <FontTablePart>().First(); var root = fontTablePart.Fonts; var docNode = doc.MainDocumentPart.Document; } //open it again, mark sure in font part, the "w14" prefix is still recognized using (WordprocessingDocument testDocument = WordprocessingDocument.Open(file, true)) { OpenXmlPart target = testDocument.MainDocumentPart.FontTablePart; using (Stream stream = target.GetStream()) using (System.Xml.XmlReader reader = System.Xml.XmlReader.Create(stream)) { reader.Read(); reader.MoveToContent(); var ns = reader.LookupNamespace("w14"); Assert.NotEqual(null, ns); } } System.IO.File.Delete(file); }