Fileupload: allow only Microsoft Office Powerpoint 2007 (pptx)

Question

Hi all

I programmed a FileUpload (C-sharp and ASP.NET) which is already working fine.

Now I'd like to add a feature: At the form where I browse for the file I want to upload, I'd like to validate the file type.

I'd like to allow only Presentation Powerpoint files in the format .pptx.

Does anybody know how i can program this feature?

I try this code, but show message: `Upload status: Only PPTX files are accepted!`

Thanks for your time and hints.