Linq----------if使用

   static void Main(string[] args)
        {
            var Spottingname = "";
            var plateno = "";
            var processid = "c8b79051249940acbeca5dd951d2c168";
            DataBaseConnect();
            List<PUNISH_ILLEGALVEHICLE_REALModel> pulist = new List<PUNISH_ILLEGALVEHICLE_REALModel>();
            using (IRepository<PUNISH_ILLEGALVEHICLE_REALModel> repository = RepositoryManager.CreateRepository<PUNISH_ILLEGALVEHICLE_REALModel>())
            {
                var list = repository.GetModels().ToList();

                //DataTable dt = ListToDt<PUNISH_ILLEGALVEHICLE_REALModel>(list);
                var q = from u in list
                        select u;
                if (!string.IsNullOrEmpty(Spottingname))
                {
                    q = q.Where(p => p.Spottingname == Spottingname);
                }
                if (!string.IsNullOrEmpty(plateno))
                {
                    q = q.Where(p => p.plateno == plateno);
                }
                if (!string.IsNullOrEmpty(processid))
                {
                    q = q.Where(p => p.processid == processid);
                }
                list = q.ToList();  //上边的所有if，只有到此处才会执行  

            }
        }