How to Save file in C#

 if (fuaudio.HasFile)

     {

      string fileextention = Path.GetExtension(fuaudio.PostedFile.FileName).ToLower().Trim();

      Audiofilename = System.DateTime.Now.ToString("dd-MM-yyyy-hh-mm-ss.fff") + fileextention;

      hdnaudio.Value = Audiofilename;

      fuaudio.SaveAs(Server.MapPath("~/Audio/" + Audiofilename));

      }