How to use power point presentation in asp.net C# ?

Note that it's not recommended to use Office Interop in ASP.NET application (see here, also technically that is also a 3th party). There is no native way to read presentation files, you'll need to use System.IO.Packaging to read PPTX files and you'll need to use System.Drawing to create/render whatever representation you want of that file (for instance convert it to an image). This is quite a large time investment so instead I would personally just convert powerpoints to pdf files in c# and send those pdf files to clients.