Add Check for empty parts to OpenXmlValidator

src/DocumentFormat.OpenXml.Framework/Packaging/OpenXmlPart.cs

@@ -448,6 +448,19 @@ internal virtual bool IsInVersion(FileFormatVersions version)
             return true;
         }
 
+        internal override bool IsEmptyPart()
+        {
+            if (!Uri.ToString().EndsWith(".xml", System.StringComparison.InvariantCultureIgnoreCase))
+            {
+                return false;
+            }
+
+            using (Stream stream = GetStream())
+            {
+                return stream.Length == 0;
+            }
+        }
+
         #endregion
 
         #region internal methods

src/DocumentFormat.OpenXml.Framework/Packaging/OpenXmlPartContainer.cs

@@ -1657,6 +1657,11 @@ internal OpenXmlPart CreateOpenXmlPart(string relationshipType)
         // find all reachable parts from the package root, the dictionary also used for cycle reference defense
         internal abstract void FindAllReachableParts(IDictionary<OpenXmlPart, bool> reachableParts);
 
+        internal virtual bool IsEmptyPart()
+        {
+            return false;
+        }
+
         #endregion
 
         // Checks if the target part is in the same OpenXmlPackage as this part.

src/DocumentFormat.OpenXml.Framework/Validation/DocumentValidator.cs

@@ -106,6 +106,19 @@ private void ValidatePart(OpenXmlPart part, ValidationContext context)
                     {
                         Validate(context);
                     }
+                    else if (part.IsEmptyPart())
+                    {
+                        context.AddError(new ValidationErrorInfo
+                        {
+                            ErrorType = ValidationErrorType.Schema,
+                            Id = "Sch_MissingPartRootElement",
+                            Part = part,
+                            Description = SR.Format(ValidationResources.Sch_MissingPartRootElement, part.Uri),
+                        });
+
+                        // The part's root element is empty, so no more errors in this part. Release the DOM to GC memory
+                        part.UnloadRootElement();
+                    }
 
                     if (!partRootElementLoaded && context.Errors.Count == lastErrorCount)
                     {

src/DocumentFormat.OpenXml.Framework/Validation/ValidationResources.resx

@@ -342,4 +342,7 @@
   <data name="Sem_CellValue" xml:space="preserve">
     <value>Cell contents have invalid value '{0}' for type '{1}'.</value>
   </data>
+  <data name="Sch_MissingPartRootElement" xml:space="preserve">
+    <value>The '{0}' part is missing its root element.</value>
+  </data>
 </root>

test/DocumentFormat.OpenXml.Tests/DocxTests01.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+using DocumentFormat.OpenXml.CustomProperties;
 using DocumentFormat.OpenXml.Packaging;
 using DocumentFormat.OpenXml.Validation;
 using System;
@@ -136,8 +137,8 @@ public void W051_AddNewPart_ToOpenXmlPackage()
             using (var stream = GetStream(TestFiles.Hyperlink, true))
             using (var doc = WordprocessingDocument.Open(stream, true))
             {
-                var pkg = (OpenXmlPackage)doc;
-                var wpcp = pkg.AddNewPart<RibbonExtensibilityPart>("application/xml", "rid1232131");
+                var footer = doc.MainDocumentPart.AddNewPart<FooterPart>();
+                footer.Footer = new W.Footer();
                 var v = new OpenXmlValidator(FileFormatVersions.Office2013);
                 var errs = v.Validate(doc, TestContext.Current.CancellationToken);
 
@@ -156,12 +157,24 @@ public void W050_DeleteAdd_CoreExtendedProperties()
 
                 doc.DeletePart(corePart);
                 doc.DeletePart(appPart);
-                doc.AddCoreFilePropertiesPart();
-                doc.AddExtendedFilePropertiesPart();
-                doc.AddCustomFilePropertiesPart();
+                var cfpp = doc.AddCoreFilePropertiesPart();
+
+                string xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?><coreProperties><title>hello</title></coreProperties>";
+                byte[] corePropsByteArray = System.Text.Encoding.UTF8.GetBytes(xml);
+                using (var stream1 = new MemoryStream(corePropsByteArray))
+                {
+                    cfpp.FeedData(stream1);
+                }
+
+                var efpp = doc.AddExtendedFilePropertiesPart();
+                efpp.Properties = new ExtendedProperties.Properties();
+
+                var cusfpp = doc.AddCustomFilePropertiesPart();
+                cusfpp.Properties = new CustomProperties.Properties();
+
                 doc.AddDigitalSignatureOriginPart();
-                doc.AddExtendedPart("relType", "contentType/xml", ".xml");
 
+                doc.AddExtendedPart("relType", "contentType/xml", ".xml");
                 var tnPart = doc.AddThumbnailPart(ThumbnailPartType.Jpeg);
                 doc.DeletePart(tnPart);
                 tnPart = doc.AddThumbnailPart("image/jpg");
@@ -180,6 +193,7 @@ public void W049_AddNewPart_ToPackage()
             using (var doc = WordprocessingDocument.Open(stream, true))
             {
                 var wpcp = doc.AddNewPart<RibbonExtensibilityPart>("application/xml", "rid1232131");
+                wpcp.CustomUI = new Office.CustomUI.CustomUI();
                 var v = new OpenXmlValidator(FileFormatVersions.Office2013);
                 var errs = v.Validate(doc, TestContext.Current.CancellationToken);
 
@@ -207,6 +221,7 @@ public void W047_AddNewPart_ToPackage()
             using (var doc = WordprocessingDocument.Open(stream, true))
             {
                 var wpcp = doc.AddNewPart<RibbonExtensibilityPart>("rid123123");
+                wpcp.CustomUI = new Office.CustomUI.CustomUI();
                 var v = new OpenXmlValidator(FileFormatVersions.Office2013);
                 var errs = v.Validate(doc, TestContext.Current.CancellationToken);
 
@@ -239,6 +254,7 @@ public void W045_AddNewPart_ToPart()
             using (var doc = WordprocessingDocument.Open(stream, true))
             {
                 var wpcp = doc.MainDocumentPart.AddNewPart<WordprocessingCommentsPart>("application/vnd.openxmlformats-officedocument.wordprocessingml.comments+xml", "rid1232131");
+                wpcp.Comments = new W.Comments();
                 var v = new OpenXmlValidator(FileFormatVersions.Office2013);
                 var errs = v.Validate(doc, TestContext.Current.CancellationToken);
 
@@ -266,6 +282,7 @@ public void W043_AddNewPart()
             using (var doc = WordprocessingDocument.Open(stream, true))
             {
                 var wpcp = doc.MainDocumentPart.AddNewPart<WordprocessingCommentsPart>("rid123123");
+                wpcp.Comments = new W.Comments();
                 var v = new OpenXmlValidator(FileFormatVersions.Office2013);
                 var errs = v.Validate(doc, TestContext.Current.CancellationToken);
 
@@ -280,6 +297,7 @@ public void W042_AddNewPart()
             using (var doc = WordprocessingDocument.Open(stream, true))
             {
                 var wpcp = doc.MainDocumentPart.AddNewPart<WordprocessingCommentsPart>();
+                wpcp.Comments = new W.Comments();
                 var v = new OpenXmlValidator(FileFormatVersions.Office2013);
                 var errs = v.Validate(doc, TestContext.Current.CancellationToken);
 

test/DocumentFormat.OpenXml.Tests/PptxTests01.cs

@@ -389,6 +389,7 @@ public void P002_Pptx_DeleteAdd_CoreExtendedProperties()
                 var corePart = doc.CoreFilePropertiesPart;
                 var appPart = doc.ExtendedFilePropertiesPart;
                 var custFilePropsPart = doc.CustomFilePropertiesPart;
+
                 var thumbNailPart = doc.ThumbnailPart;
 
                 doc.DeletePart(corePart);
@@ -399,9 +400,96 @@ public void P002_Pptx_DeleteAdd_CoreExtendedProperties()
                     doc.DeletePart(thumbNailPart);
                 }
 
-                doc.AddCoreFilePropertiesPart();
-                doc.AddExtendedFilePropertiesPart();
-                doc.AddCustomFilePropertiesPart();
+                var coreFPP = doc.AddCoreFilePropertiesPart();
+                var coreFPPStream = coreFPP.GetStream();
+                using (var writer = new System.Xml.XmlTextWriter(coreFPPStream, System.Text.Encoding.UTF8))
+                {
+                    writer.WriteRaw("""
+                        <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+                        <cp:coreProperties xmlns:cp="http://schemas.openxmlformats.org/package/2006/metadata/core-properties" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:dcmitype="http://purl.org/dc/dcmitype/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+                          <dc:title></dc:title>
+                          <dc:creator>Joey Daccord</dc:creator>
+                          <cp:lastModifiedBy>Joey Daccord</cp:lastModifiedBy>
+                          <cp:revision>2</cp:revision>
+                          <dcterms:created xsi:type="dcterms:W3CDTF">2025-06-12T19:21:34Z</dcterms:created>
+                          <dcterms:modified xsi:type="dcterms:W3CDTF">2025-06-12T21:23:11Z</dcterms:modified>
+                        </cp:coreProperties>
+                        """);
+                    writer.Flush();
+                }
+
+                var appFPP = doc.AddExtendedFilePropertiesPart();
+                var appFPPStream = appFPP.GetStream();
+                using (var writer = new System.Xml.XmlTextWriter(appFPPStream, System.Text.Encoding.UTF8))
+                {
+                    writer.WriteRaw("""
+                        <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+                        <Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/extended-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes">
+                          <TotalTime>12</TotalTime>
+                          <Words>0</Words>
+                          <Application>Microsoft Office PowerPoint</Application>
+                          <PresentationFormat>Widescreen</PresentationFormat>
+                          <Paragraphs>0</Paragraphs>
+                          <Slides>1</Slides>
+                          <Notes>0</Notes>
+                          <HiddenSlides>0</HiddenSlides>
+                          <MMClips>0</MMClips>
+                          <ScaleCrop>false</ScaleCrop>
+                          <HeadingPairs>
+                            <vt:vector size="6" baseType="variant">
+                              <vt:variant>
+                                <vt:lpstr>Fonts Used</vt:lpstr>
+                              </vt:variant>
+                              <vt:variant>
+                                <vt:i4>3</vt:i4>
+                              </vt:variant>
+                              <vt:variant>
+                                <vt:lpstr>Theme</vt:lpstr>
+                              </vt:variant>
+                              <vt:variant>
+                                <vt:i4>1</vt:i4>
+                              </vt:variant>
+                              <vt:variant>
+                                <vt:lpstr>Slide Titles</vt:lpstr>
+                              </vt:variant>
+                              <vt:variant>
+                                <vt:i4>1</vt:i4>
+                              </vt:variant>
+                            </vt:vector>
+                          </HeadingPairs>
+                          <TitlesOfParts>
+                            <vt:vector size="5" baseType="lpstr">
+                              <vt:lpstr>Aptos</vt:lpstr>
+                              <vt:lpstr>Aptos Display</vt:lpstr>
+                              <vt:lpstr>Arial</vt:lpstr>
+                              <vt:lpstr>Office Theme</vt:lpstr>
+                              <vt:lpstr>PowerPoint Presentation</vt:lpstr>
+                            </vt:vector>
+                          </TitlesOfParts>
+                          <Company></Company>
+                          <LinksUpToDate>false</LinksUpToDate>
+                          <SharedDoc>false</SharedDoc>
+                          <HyperlinksChanged>false</HyperlinksChanged>
+                          <AppVersion>16.0000</AppVersion>
+                        </Properties>
+                        """);
+                }
+
+                var custFPP = doc.AddCustomFilePropertiesPart();
+                var custFPPStream = custFPP.GetStream();
+                using (var writer = new System.Xml.XmlTextWriter(custFPPStream, System.Text.Encoding.UTF8))
+                {
+                    writer.WriteRaw("""
+                        <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+                        <Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/custom-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes">
+                          <property fmtid="{D5CDD505-2E9C-101B-9397-08002B2CF9AE}" pid="2" name="MyCustomProp">
+                            <vt:lpwstr>foobar</vt:lpwstr>
+                          </property>
+                        </Properties>
+                        """);
+                    writer.Flush();
+                }
+
                 doc.AddDigitalSignatureOriginPart();
                 doc.AddExtendedPart("relType", "contentType/xml", ".xml");
 

test/DocumentFormat.OpenXml.Tests/XlsxTests01.cs

@@ -67,9 +67,78 @@ public void X006_Xlsx_DeleteAdd_CoreExtendedProperties()
                 var appPart = doc.ExtendedFilePropertiesPart;
                 doc.DeletePart(corePart);
                 doc.DeletePart(appPart);
-                doc.AddCoreFilePropertiesPart();
-                doc.AddExtendedFilePropertiesPart();
-                doc.AddCustomFilePropertiesPart();
+                var cFPP = doc.AddCoreFilePropertiesPart();
+                var cFPPStream = cFPP.GetStream();
+
+                using (var writer = new System.Xml.XmlTextWriter(cFPPStream, System.Text.Encoding.UTF8))
+                {
+                    writer.WriteRaw("""
+                        <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+                        <cp:coreProperties xmlns:cp="http://schemas.openxmlformats.org/package/2006/metadata/core-properties" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:dcmitype="http://purl.org/dc/dcmitype/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+                          <dc:creator>Shohei Ohtani</dc:creator>
+                          <cp:lastModifiedBy>Shohei Ohtani</cp:lastModifiedBy>
+                          <dcterms:created xsi:type="dcterms:W3CDTF">2015-06-05T18:17:20Z</dcterms:created>
+                          <dcterms:modified xsi:type="dcterms:W3CDTF">2025-06-13T17:11:50Z</dcterms:modified>
+                        </cp:coreProperties>
+                        """);
+
+                    writer.Flush();
+                }
+
+                var eFPP = doc.AddExtendedFilePropertiesPart();
+                var eFPPStream = eFPP.GetStream();
+
+                using (var writer = new System.Xml.XmlTextWriter(eFPPStream, System.Text.Encoding.UTF8))
+                {
+                    writer.WriteRaw("""
+                        <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+                        <Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/extended-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes">
+                          <Application>Microsoft Excel</Application>
+                          <DocSecurity>0</DocSecurity>
+                          <ScaleCrop>false</ScaleCrop>
+                          <HeadingPairs>
+                            <vt:vector size="2" baseType="variant">
+                              <vt:variant>
+                                <vt:lpstr>Worksheets</vt:lpstr>
+                              </vt:variant>
+                              <vt:variant>
+                                <vt:i4>1</vt:i4>
+                              </vt:variant>
+                            </vt:vector>
+                          </HeadingPairs>
+                          <TitlesOfParts>
+                            <vt:vector size="1" baseType="lpstr">
+                              <vt:lpstr>Sheet1</vt:lpstr>
+                            </vt:vector>
+                          </TitlesOfParts>
+                          <Company></Company>
+                          <LinksUpToDate>false</LinksUpToDate>
+                          <SharedDoc>false</SharedDoc>
+                          <HyperlinksChanged>false</HyperlinksChanged>
+                          <AppVersion>16.0300</AppVersion>
+                        </Properties>
+                        """);
+
+                    writer.Flush();
+                }
+
+                var custFPP = doc.AddCustomFilePropertiesPart();
+                var custFPPStream = custFPP.GetStream();
+
+                using (var writer = new System.Xml.XmlTextWriter(custFPPStream, System.Text.Encoding.UTF8))
+                {
+                    writer.WriteRaw("""
+                        <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+                        <Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/custom-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes">
+                          <property fmtid="{D5CDD505-2E9C-101B-9397-08002B2CF9AE}" pid="2" name="MyCustomProp">
+                            <vt:lpwstr>tacocat</vt:lpwstr>
+                          </property>
+                        </Properties>
+                        """);
+
+                    writer.Flush();
+                }
+
                 doc.AddDigitalSignatureOriginPart();
                 doc.AddExtendedPart("relType", "contentType/xml", ".xml");
                 var tnPart = doc.AddThumbnailPart(ThumbnailPartType.Jpeg);

test/DocumentFormat.OpenXml.Tests/ofapiTest/OpenXmlValidatorTest.cs

@@ -3832,5 +3832,23 @@ public void VersionMismatchPartValidatingTest()
                 Assert.Throws<System.InvalidOperationException>(() => O14Validator.Validate(wordTestDocument.MainDocumentPart, TestContext.Current.CancellationToken));
             }
         }
+
+        [Fact]
+        public void EmptyPartRootElementValidatingTest()
+        {
+            using (Stream stream = new MemoryStream())
+            using (WordprocessingDocument document = WordprocessingDocument.Create(stream, WordprocessingDocumentType.Document))
+            {
+                document.AddMainDocumentPart();
+
+                IEnumerable<ValidationErrorInfo> errors = O14Validator.Validate(document, TestContext.Current.CancellationToken);
+                ValidationErrorInfo info = errors.FirstOrDefault();
+
+                Assert.Single(errors);
+                Assert.Equal("Sch_MissingPartRootElement", info.Id);
+                Assert.Equal("The '/word/document.xml' part is missing its root element.", info.Description);
+                Assert.Equal(ValidationErrorType.Schema, info.ErrorType);
+            }
+        }
     }
 }