I have the code below where I try copying the slides from one ppt to another. I do this because the second ppt already has the logic implemented in another area of the application and now I want to join the slides to the current one to have all the information available if desired.

The real problem that I have is when the second ppt contains more than one slide I will get the error that appeared in the picture when opening the final report.

It is important to mention that for a single slide everything works correctly, the slides having basically the same content, so I don’t think it has to do with lack of information.

 public ReportResult ExportEVReportToPowerPointFile(EVReport evReportData, string exportLanguage, string currentRequestUrl, MemoryStream topIssueStream)
        {
            var folderPath = _folderPathRepository.GetByCode($"EV-Report-{exportLanguage.ToUpperInvariant()}");
            var reportTemplatePath = folderPath?.Path;

            if (string.IsNullOrEmpty(reportTemplatePath))
            {
                return null;
            }

            var reportMS = _generateEVStatusReportService.ExportEVReportToPowerPointFile(evReportData, reportTemplatePath, exportLanguage, currentRequestUrl);

            using (var reportPresentation = PresentationDocument.Open(reportMS, true))
            using (var topIssuePresentation = PresentationDocument.Open(topIssueStream, true))
            {
                var reportPresentationPart = reportPresentation.PresentationPart;
                var slideIdList = reportPresentationPart.Presentation.SlideIdList;
                uint maxSlideId = slideIdList.ChildElements.Cast<SlideId>().Max(s => s.Id.Value);

                foreach (var topIssueSlidePart in topIssuePresentation.PresentationPart.SlideParts)
                {
                    // Clone the entire slide
                    CloneSlide(topIssueSlidePart, reportPresentationPart);

                    // Add the slide to the SlideIdList
                    var slideId = slideIdList.AppendChild(new SlideId());
                    slideId.Id = ++maxSlideId;
                    slideId.RelationshipId = reportPresentationPart.GetIdOfPart(reportPresentationPart.SlideParts.Last());
                }

                reportPresentation.Save();
            }

            var result = new ReportResult
            {
                RootPath = reportTemplatePath,
                FilePath = reportTemplatePath,
                Filename = evReportData.IsSnapshot ? $"EV_Snapshot_{DateTime.Now:dd_MM_yyyy}" : $"EV_Status_{DateTime.Now:dd_MM_yyyy}",
                Base64EncodedFile = Convert.ToBase64String(reportMS.ToArray(), Base64FormattingOptions.None)
            };

            return result;
        }


        private void CloneSlide(SlidePart sourceSlidePart, PresentationPart destinationPresentationPart)
        {
            // Create a new slide part in the destination presentation
            var newSlidePart = destinationPresentationPart.AddNewPart<SlidePart>();

            // Copy the slide content
            newSlidePart.FeedData(sourceSlidePart.GetStream());

            // Copy the slide layout and its dependencies
            if (sourceSlidePart.SlideLayoutPart != null)
            {
                SlideLayoutPart newSlideLayoutPart = GetOrCreateSlideLayoutPart(sourceSlidePart.SlideLayoutPart, destinationPresentationPart);

                // Add the slide layout part to the new slide part
                newSlidePart.AddPart(newSlideLayoutPart);
            }

            // Clone other related parts and their relationships
            foreach (var part in sourceSlidePart.Parts)
            {
                if (!(part.OpenXmlPart is SlideLayoutPart))
                {
                    var clonedPart = newSlidePart.AddPart(part.OpenXmlPart, part.RelationshipId);
                    clonedPart.FeedData(part.OpenXmlPart.GetStream());
                }
            }
        }

        private SlideLayoutPart GetOrCreateSlideLayoutPart(SlideLayoutPart sourceSlideLayoutPart, PresentationPart destinationPresentationPart)
        {
            SlideMasterPart sourceSlideMasterPart = sourceSlideLayoutPart.SlideMasterPart;
            SlideMasterPart destinationSlideMasterPart = GetOrCreateSlideMasterPart(sourceSlideMasterPart, destinationPresentationPart);

            // Find or create the slide layout part
            SlideLayoutPart newSlideLayoutPart = destinationSlideMasterPart.SlideLayoutParts
                .FirstOrDefault(slp => slp.Uri == sourceSlideLayoutPart.Uri);

            if (newSlideLayoutPart == null)
            {
                newSlideLayoutPart = destinationSlideMasterPart.AddNewPart<SlideLayoutPart>();
                newSlideLayoutPart.FeedData(sourceSlideLayoutPart.GetStream());

                // Clone related parts like images, charts, etc.
                foreach (var part in sourceSlideLayoutPart.Parts)
                {
                    var clonedPart = newSlideLayoutPart.AddPart(part.OpenXmlPart, part.RelationshipId);
                    clonedPart.FeedData(part.OpenXmlPart.GetStream());
                }
            }

            return newSlideLayoutPart;
        }

        private SlideMasterPart GetOrCreateSlideMasterPart(SlideMasterPart sourceSlideMasterPart, PresentationPart destinationPresentationPart)
        {
            // Find or create the slide master part
            SlideMasterPart newSlideMasterPart = destinationPresentationPart.SlideMasterParts
                .FirstOrDefault(smp => smp.Uri == sourceSlideMasterPart.Uri);

            if (newSlideMasterPart == null)
            {
                newSlideMasterPart = destinationPresentationPart.AddNewPart<SlideMasterPart>();
                newSlideMasterPart.FeedData(sourceSlideMasterPart.GetStream());

                // Clone related parts like themes, fonts, etc.
                foreach (var part in sourceSlideMasterPart.Parts)
                {
                    var clonedPart = newSlideMasterPart.AddPart(part.OpenXmlPart, part.RelationshipId);
                    clonedPart.FeedData(part.OpenXmlPart.GetStream());
                }
            }

            return newSlideMasterPart;
        }