IIS 8.5 / later upload config

protected void Button1_Click(object sender, EventArgs e)
        {
            string FilePath = FileUpload1.FileName;
            //verify the file whether is exist
            if (FileUpload1.HasFile)
            {
                //verify the file's type
                if (System.IO.Path.GetExtension(FilePath) != ".jpg")
                {
                    Response.Write("<script>alert('The fiel type not right !')</script>");
                }
                else
                {
                    FileUpload1.PostedFile.SaveAs(Server.MapPath("~/Files/NewFile.jpg"));
                    Response.Write("<script>alert('Success !')</script>");
                }
            }
            else
            {
                Response.Write("<script>alert('The fiel is not exist !')</script>");
            }
        }