class Program
    {
        static void Main(string[] args)
        {
            InsertNewSlide(@"..\..\Documents\Myppt2.pptx", 1, "My new slide");
        }
        // Insert a slide into the specified presentation.
        public static void InsertNewSlide(string presentationFile, int position, string slideTitle)
        {
            // Open the source document as read/write. 
            using (PresentationDocument presentationDocument = PresentationDocument.Open(presentationFile, true))
            {
                // Pass the source document and the position and title of the slide to be inserted to the next method.
                InsertNewSlide(presentationDocument, position, slideTitle);
            }
        }

        // Insert the specified slide into the presentation at the specified position.
        public static void InsertNewSlide(PresentationDocument presentationDocument, int position, string slideTitle)
        {

            if (presentationDocument == null)
            {
                throw new ArgumentNullException("presentationDocument");
            }

            if (slideTitle == null)
            {
                throw new ArgumentNullException("slideTitle");
            }

            PresentationPart presentationPart = presentationDocument.PresentationPart;

            // Verify that the presentation is not empty.
            if (presentationPart == null)
            {
                throw new InvalidOperationException("The presentation document is empty.");
            }

            // Declare and instantiate a new slide.
            Slide slide = new Slide(new CommonSlideData(new ShapeTree()));
            uint drawingObjectId = 1;

            // Construct the slide content.            
            // Specify the non-visual properties of the new slide.
            NonVisualGroupShapeProperties nonVisualProperties = slide.CommonSlideData.ShapeTree.AppendChild(new NonVisualGroupShapeProperties());
            nonVisualProperties.NonVisualDrawingProperties = new NonVisualDrawingProperties() { Id = 1, Name = "" };
            nonVisualProperties.NonVisualGroupShapeDrawingProperties = new NonVisualGroupShapeDrawingProperties();
            nonVisualProperties.ApplicationNonVisualDrawingProperties = new ApplicationNonVisualDrawingProperties();

            // Specify the group shape properties of the new slide.
            slide.CommonSlideData.ShapeTree.AppendChild(new GroupShapeProperties());

            // Declare and instantiate the title shape of the new slide.
            Shape titleShape = slide.CommonSlideData.ShapeTree.AppendChild(new Shape());

            drawingObjectId++;

            // Specify the required shape properties for the title shape. 
            titleShape.NonVisualShapeProperties = new NonVisualShapeProperties
                (new NonVisualDrawingProperties() { Id = drawingObjectId, Name = "Title" },
                new NonVisualShapeDrawingProperties(new Drawing.ShapeLocks() { NoGrouping = true }),
                new ApplicationNonVisualDrawingProperties(new PlaceholderShape() { Type = PlaceholderValues.Title }));
            titleShape.ShapeProperties = new ShapeProperties();

            // Specify the text of the title shape.
            titleShape.TextBody = new TextBody(new Drawing.BodyProperties(),
                    new Drawing.ListStyle(),
                    new Drawing.Paragraph(new Drawing.Run(new Drawing.Text() { Text = slideTitle })));

            // Declare and instantiate the body shape of the new slide.
            Shape bodyShape = slide.CommonSlideData.ShapeTree.AppendChild(new Shape());
            drawingObjectId++;

            // Specify the required shape properties for the body shape.
            bodyShape.NonVisualShapeProperties = new NonVisualShapeProperties(new NonVisualDrawingProperties() { Id = drawingObjectId, Name = "Content Placeholder" },
                    new NonVisualShapeDrawingProperties(new Drawing.ShapeLocks() { NoGrouping = true }),
                    new ApplicationNonVisualDrawingProperties(new PlaceholderShape() { Index = 1 }));
            bodyShape.ShapeProperties = new ShapeProperties();

            // Specify the text of the body shape.
            bodyShape.TextBody = new TextBody(new Drawing.BodyProperties(),
                    new Drawing.ListStyle(),
                    new Drawing.Paragraph());

            // Create the slide part for the new slide.
            SlidePart slidePart = presentationPart.AddNewPart();

            // Save the new slide part.
            slide.Save(slidePart);

            // Modify the slide ID list in the presentation part.
            // The slide ID list should not be null.
            SlideIdList slideIdList = presentationPart.Presentation.SlideIdList;

            // Find the highest slide ID in the current list.
            uint maxSlideId = 1;
            SlideId prevSlideId = null;

            foreach (SlideId slideId in slideIdList.ChildElements)
            {
                if (slideId.Id > maxSlideId)
                {
                    maxSlideId = slideId.Id;
                }

                position--;
                if (position == 0)
                {
                    prevSlideId = slideId;
                }

            }

            maxSlideId++;

            // Get the ID of the previous slide.
            SlidePart lastSlidePart;

            if (prevSlideId != null)
            {
                lastSlidePart = (SlidePart)presentationPart.GetPartById(prevSlideId.RelationshipId);
            }
            else
            {
                lastSlidePart = (SlidePart)presentationPart.GetPartById(((SlideId)(slideIdList.ChildElements[0])).RelationshipId);
            }

            // Use the same slide layout as that of the previous slide.
            if (null != lastSlidePart.SlideLayoutPart)
            {
                slidePart.AddPart(lastSlidePart.SlideLayoutPart);
            }

            // Insert the new slide into the slide list after the previous slide.
            SlideId newSlideId = slideIdList.InsertAfter(new SlideId(), prevSlideId);
            newSlideId.Id = maxSlideId;
            newSlideId.RelationshipId = presentationPart.GetIdOfPart(slidePart);

            // Save the modified presentation.
            presentationPart.Presentation.Save();
        }

    }

class Program
    {
        static void Main(string[] args)
        {
            InsertNewSlide(@"..\..\Documents\Myppt2.pptx", 1, "My new slide");
        }
        public static void InsertNewSlide(string presentationFile, int position, string slideTitle)
        {

            //Initialize an instances of Presentation class and load the sample PowerPoint file
            Presentation presentation = new Presentation();
            presentation.LoadFromFile(presentationFile);

            //Add a new slide by position
            presentation.Slides.Insert(position);

            //Add a shape to the new slide and then add some text to the shape 
            RectangleF rect = new RectangleF(0, 0, presentation.SlideSize.Size.Width, presentation.SlideSize.Size.Height);
            IAutoShape shape = presentation.Slides[position].Shapes.AppendShape(ShapeType.Rectangle, new RectangleF(50, 150, 600, 200));
            shape.AppendTextFrame(slideTitle);

            //Save PPT document
            presentation.SaveToFile(@"..\..\Documents\result.pptx", FileFormat.Pptx2010);
        }
    }