Delete a slide from a presentation

class Program
    {
        static void Main(string[] args)
        {
            DeleteSlide(@"..\..\Documents\Myppt5.pptx", 2);
            Console.WriteLine("Number of slides = {0}",CountSlides(@"..\..\Documents\Myppt5.pptx"));
        }
        // Get the presentation object and pass it to the next CountSlides method.
        public static int CountSlides(string presentationFile)
        {
            // Open the presentation as read-only.
            using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, false))
            {
                // Pass the presentation to the next CountSlide method
                // and return the slide count.
                return CountSlides(presentationDocument);
            }
        }

        // Count the slides in the presentation.
        public static int CountSlides(PresentationDocument presentationDocument)
        {
            // Check for a null document object.
            if (presentationDocument == null)
            {
                throw new ArgumentNullException("presentationDocument");
            }

            int slidesCount = 0;

            // Get the presentation part of document.
            PresentationPart presentationPart = presentationDocument.PresentationPart;

            // Get the slide count from the SlideParts.
            if (presentationPart != null)
            {
                slidesCount = presentationPart.SlideParts.Count();
            }

            // Return the slide count to the previous method.
            return slidesCount;
        }
        //
        // Get the presentation object and pass it to the next DeleteSlide method.
        public static void DeleteSlide(string presentationFile, int slideIndex)
        {
            // Open the source document as read/write.

            using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, true))
            {
                // Pass the source document and the index of the slide to be deleted to the next DeleteSlide method.
                DeleteSlide(presentationDocument, slideIndex);
            }
        }

        // Delete the specified slide from the presentation.
        public static void DeleteSlide(PresentationDocument presentationDocument, int slideIndex)
        {
            if (presentationDocument == null)
            {
                throw new ArgumentNullException("presentationDocument");
            }

            // Use the CountSlides sample to get the number of slides in the presentation.
            int slidesCount = CountSlides(presentationDocument);

            if (slideIndex < 0 || slideIndex >= slidesCount)
            {
                throw new ArgumentOutOfRangeException("slideIndex");
            }

            // Get the presentation part from the presentation document. 
            PresentationPart presentationPart = presentationDocument.PresentationPart;

            // Get the presentation from the presentation part.
            Presentation presentation = presentationPart.Presentation;

            // Get the list of slide IDs in the presentation.
            SlideIdList slideIdList = presentation.SlideIdList;

            // Get the slide ID of the specified slide
            SlideId slideId = slideIdList.ChildElements[slideIndex] as SlideId;

            // Get the relationship ID of the slide.
            string slideRelId = slideId.RelationshipId;

            // Remove the slide from the slide list.
            slideIdList.RemoveChild(slideId);

            //
            // Remove references to the slide from all custom shows.
            if (presentation.CustomShowList != null)
            {
                // Iterate through the list of custom shows.
                foreach (var customShow in presentation.CustomShowList.Elements())
                {
                    if (customShow.SlideList != null)
                    {
                        // Declare a link list of slide list entries.
                        LinkedList slideListEntries = new LinkedList();
                        foreach (SlideListEntry slideListEntry in customShow.SlideList.Elements())
                        {
                            // Find the slide reference to remove from the custom show.
                            if (slideListEntry.Id != null && slideListEntry.Id == slideRelId)
                            {
                                slideListEntries.AddLast(slideListEntry);
                            }
                        }

                        // Remove all references to the slide from the custom show.
                        foreach (SlideListEntry slideListEntry in slideListEntries)
                        {
                            customShow.SlideList.RemoveChild(slideListEntry);
                        }
                    }
                }
            }

            // Save the modified presentation.
            presentation.Save();

            // Get the slide part for the specified slide.
            SlidePart slidePart = presentationPart.GetPartById(slideRelId) as SlidePart;

            // Remove the slide part.
            presentationPart.DeletePart(slidePart);
        }
    }