hello,
a slide and positioning it to the end of the presentation
//Instantiate PresentationEx class that represents a PPTX file
PresentationEx pres = new PresentationEx("d:\\pptx\\helloworld.pptx");
//Clone the desired slide to the end of the collection of slides in the same PPTX
SlidesEx slds = pres.Slides;
slds.AddClone(pres.Slides[0]);
//Write the modified pptx to disk
pres.Write("d:\\pptx\\helloworld_cloned.pptx"); // <>>
please advice.