Response to: What is the code for FileUpload of pptx files

if (UploadIcon.HasFile)
        {
                string strFileExtension = Path.GetExtension(UploadIcon.PostedFile.FileName);
                if (strFileExtension != null)
                {
                    string validFileExtension = strFileExtension.ToLower();
                    if (validFileExtension == ".pptx")
                    {
                            string filepath = Server.MapPath("~/Images");
                            if (!Directory.Exists(filepath ))
                            {
                                Directory.CreateDirectory(imagePath);
                            }
                            string fileName = Guid.NewGuid().ToString().Replace("-", "") + strFileExtension; //to generate unique file name
                            UploadIcon.SaveAs(filepath  + "/" + fileName);

                    }
                    else
                    {
                        lblMessage.Text = Common.DisplayMessage("Please upload only jpg, jpeg, gif, png format",
                                                                MessageType.ErrorMessage, 5, DisplayStyle.None);
                        return;
                    }
              }
    }