how to delete files from existing folder before uploading files

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {        
   //Deleting older files in "NewFolder1".

            foreach (var f in System.IO.Directory.GetFiles(Server.MapPath("~/NewFolder1")))

            System.IO.File.Delete(f);
        }
    }