将语法更改为Linq to SQL lambda join
我想将我的linq语句从查询语法切换到lambda,对我来说,最难理解的是lambda join
from ru in db.rpm_usr join ei in db.emp_info on ru.wwid equals ei.wwid
所以上面的查询连接语法很简单,但是当我尝试将它放入lambda时
这不适合我
.Join(Rpm_scrty_emp_info, p => p.Iact_ind, j => j.Wwid
完整查询:
var queryAllUsers = (from ru in db.rpm_usr join ei in db.emp_info on ru.wwid equals ei.wwid let cdis_eml = ei.dmn_addr + ";" where ru.inact_ind == "N" && ei.inact_ind == "N" && ei.dmn_addr != null orderby ei.dmn_addr select new rpm_scrty_rpm_usr() { usr_id = ru.usr_id, usr_lnm = ru.usr_lnm, usr_pwd = ru.usr_pwd, usr_fnm = ru.usr_fnm, wwid = ru.wwid, apprvr_wwid = ru.apprvr_wwid, chg_dtm = ru.chg_dtm, chg_usr_id = ru.chg_usr_id, dflt_ste_id = ru.dflt_ste_id, cre_dtm = ru.cre_dtm, cre_usr_id = ru.cre_usr_id, lst_pwd_chg_dtm = ru.lst_pwd_chg_dtm, lst_accs_dtm = ru.lst_accs_dtm, email_id = ru.email_id, inact_ind = ru.inact_ind, salt = ru.salt, tel = ru.tel }).ToList();
我个人发现通过将查询分解为单独的行来更容易理解LINQ的点符号。
继上面的@Tom的例子之后,查询分解如下:
user.Join(Rpm_scrty_emp_info, // We want to join user to Rpm_scrty_emp_info z => z.Wwid, // On the left "user" side of the join we want to use the Wwid property ei => ei.Wwid, // On the right "employee info" side of the join we want to use the Wwid property (z, ei) => z) // We then want to return the results on the left side of the join, ie our z objects
您还可以关注@ Tom的第一个示例,并利用匿名对象返回连接的两侧,甚至是特定属性。
如果您还没有,我强烈推荐使用LINQpad软件。 它非常适合调试LINQ,还有一个用于在查询和lambda语法之间切换的内置转换器。
我不确定它真的“值得”它因为lambda加入我并不漂亮,就像这样。
我错了,这将解决Anonymous Type issue
不要这样做
.Join (db.emp_info, ru => ru.wwid, ei => ei.wwid, (ru, ei) => new { ru = ru, ei = ei })
INSTEAD DO THIS
.Join(Rpm_scrty_emp_info, z => z.Wwid, ei => ei.Wwid, (z, ei) => z)