Fix data part references

src/DocumentFormat.OpenXml/Packaging/OpenXmlPartContainer.cs

@@ -1698,6 +1698,7 @@ private OpenXmlPart AddSubPartFromOtherPackage(OpenXmlPart part, IDictionary<Ope
                     }
                 }
 
+                var updatedParts = new Dictionary<DataPart, DataPart>();
                 foreach (var item in dataPartsDictionary)
                 {
                     if (item.Value is null)
@@ -1714,17 +1715,21 @@ private OpenXmlPart AddSubPartFromOtherPackage(OpenXmlPart part, IDictionary<Ope
 
                         InternalOpenXmlPackage.AddDataPartToList(newDataPart);
 
-                        dataPartsDictionary[dataPart] = newDataPart;
+                        updatedParts.Add(dataPart, newDataPart);
                     }
                 }
 
+                foreach (var item in updatedParts) {
+                    dataPartsDictionary[item.Key] = item.Value;
+                }
+
                 // then create data part reference relationship
                 foreach (var dataPartReferenceRelationship in part.DataPartReferenceRelationships)
                 {
                     if (dataPartsDictionary[dataPartReferenceRelationship.DataPart] is MediaDataPart newDataPart)
                     {
-                        var newDataPartReference = DataPartReferenceRelationship.Create(this, newDataPart, dataPartReferenceRelationship.RelationshipType, dataPartReferenceRelationship.Id);
-                        ReferenceRelationshipList.AddLast(newDataPartReference);
+                        var newDataPartReference = DataPartReferenceRelationship.Create(child, newDataPart, dataPartReferenceRelationship.RelationshipType, dataPartReferenceRelationship.Id);
+                        child.AddDataPartReferenceRelationship(newDataPartReference);
                     }
                 }
 

test/DocumentFormat.OpenXml.Packaging.Tests/OpenXmlPackageTests.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.Presentation;
 using DocumentFormat.OpenXml.Wordprocessing;
 using System;
 using System.Collections.Generic;
@@ -9,6 +10,8 @@
 using System.Xml.Linq;
 using Xunit;
 
+using Text = DocumentFormat.OpenXml.Wordprocessing.Text;
+
 namespace DocumentFormat.OpenXml.Packaging.Tests
 {
     public class OpenXmlPackageTests
@@ -208,5 +211,49 @@ public void CanTransformWordprocessingDocumentWithAltChunksToFlatOpc()
                 Assert.All(altChunkParts, p => Assert.NotEmpty(p.Elements(Pkg + "binaryData")));
             }
         }
+
+        private static MemoryStream CreatePresentationDocumentWithDataReference()
+        {
+            var stream = new MemoryStream();
+
+            using (var ppt = PresentationDocument.Create(stream, PresentationDocumentType.Presentation))
+            {
+                var mainPart = ppt.AddPresentationPart();
+                var slide = new Slide();
+                var slidePart = mainPart.AddNewPart<SlidePart>();
+                var dataPart = new MediaDataPart(ppt.InternalOpenXmlPackage, MediaDataPartType.Mp3);
+                var dataPartReferenceRelationship = DataPartReferenceRelationship.Create(slidePart, dataPart, MediaReferenceRelationship.RelationshipTypeConst, "rId2");
+                slidePart.AddDataPartReferenceRelationship(dataPartReferenceRelationship);
+                slide.Save(slidePart);
+                mainPart.Presentation = new Presentation.Presentation(slide);
+                mainPart.Presentation.Save();
+            }
+
+            stream.Seek(0, SeekOrigin.Begin);
+            return stream;
+        }
+
+        // This is a regression test case for issue #931
+        // Saving a office documents opened using the OpenXML SDK removed data references from the saved document.
+        // This lead to invalid documents that couldn't be opened by office.
+        [Fact]
+        public void TestDataReferenceRelationshipsAreClonedCorrectly()
+        {
+            using var stream = CreatePresentationDocumentWithDataReference();
+            using var ppt = PresentationDocument.Open(stream, false);
+            Assert.NotNull(ppt.PresentationPart);
+            Assert.NotNull(ppt.PresentationPart.Presentation);
+            Assert.Single(ppt.PresentationPart.SlideParts);
+            var slidePart = ppt.PresentationPart.SlideParts.First();
+            Assert.NotEmpty(slidePart.DataPartReferenceRelationships);
+            var clonedStream = new MemoryStream();
+            ppt.Clone(clonedStream);
+            using var clonedPpt = PresentationDocument.Open(clonedStream, false);
+            Assert.NotNull(clonedPpt.PresentationPart);
+            Assert.NotNull(clonedPpt.PresentationPart.Presentation);
+            Assert.Single(clonedPpt.PresentationPart.SlideParts);
+            var clonedSlidePart = clonedPpt.PresentationPart.SlideParts.First();
+            Assert.NotEmpty(clonedSlidePart.DataPartReferenceRelationships);
+        }
     }
 }