List<int> id_list = new List<int>() { 1 };//测试数据...

List<string> guid_list = (from uinfo in db.UserInfo

                                          where id_list.Contains(uinfo.ID)

                                          select new

                                          {

                                              uid= uinfo.Guid

                                          }).ToList().Select(u => u.uid).ToList<string>();