c# var sql 方式查询的方式，请教这是什么意思

Question

public void AddApply(JQ_D_DeviceInfo a, List l)
{
var q_rs = (from n in db.JQ_D_DeviceInfo
where n.deviceNo == a.deviceNo
select new { n.id }).ToList();
b.JQ_D_DeviceInfo.InsertOnSubmit(a);
db.SubmitChanges();

        int deviceNo = (from n in db.JQ_D_DeviceInfo
                        where n.id == a.id
                        select new { n.id }).ToList()[0].id;
        string sql1 = "delete from JQ_D_DeviceInfo where id = {0}";
        db.ExecuteCommand(sql1, deviceNo);
        foreach (var item in l)
        {
            string sql2 = "insert into JQ_D_DeviceInfo(deviceNo,devicename,devicetype,deviceuser,fzrmoblie,devicefirm,firmmobile,booker,booktime,deviceadd,logindate) values ({0},{1},{2},{3},{4},{5},{6},{7},{8},{9},{10}})";
            db.ExecuteCommand(sql2, item.deviceNo, item.devicename, item.devicetype, item.deviceuser, item.fzrmoblie, item.devicefirm, item.firmmobile, item.booker, item.booktime, item.deviceadd, item.logindate);
        }

这段代码开头的查询方式是什么意思，请教一下

Answer 1

这是LINQ的写法
就是查询出db.JQ_D_DeviceInfo中和a中所有deviceNo相等的记录，然后取db.JQ_D_DeviceInfo中id的集合，然后转化成List