public void addGuestRequest(GuestRequest r) { var v = from item in dal.GetGuestRequestList() where item.ID == r.ID && (item.PrivateName != r.PrivateName || item.FamilyName != r.FamilyName) select item; foreach (GuestRequest item in v) { } if (v != null) { if (r.EntryDate.Date >= r.ReleaseDate.Date) { throw new Exception("entry date must be smaller than the release day at least one day"); } else { try { if (r.MailAddress.EndsWith("@gmail.com")) { r.RegistrationDate = DateTime.Now; dal.addGuestRequest(r); } else { throw new Exception("bl:addGuestRequest:the mail address is not correct"); } } catch (Exception x) { throw new Exception(x.Message); } } } else { throw new Exception("bl:addGuestRequest:the id is not taken allready"); } }