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  • Linq查询Specified cast is not valid异常的常见原因

    Linq查询Specified cast is not valid异常的常见原因一。异常原因“System.InvalidCastException:Specified cast is not valid”Linq to SQL查询出现以上异常,通常是因为Model文件中相关表的字段类型和数据库对应表的字段类型不一致引起的。 二。处理办法:1)检查Model…

    2021/8/12 20:55:26
  • The specified type member 'Date' is not supported in LINQ to Entities.

    LINQ中不能直接使用DateTime,否则会报错:‘The specified type member Date is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are support’需要把DateTime定义在LINQ之外,例如: var now = D…

    2021/2/21 19:37:57
  • LINQ的写法—sql中通过Join连接两个表并关联多个条件

    1、sql语句:select * from Users u join Teachers t on u.UserID==t.TeacherID and u.Name=t.Name2、linq写法:方法一:var userInfos = from u in db.Users join t in db.Teachers on new { u.UserID , u.Name } equals new { UserID = t.TeacherID,t.Name } s…

    2021/2/21 19:35:48
  • LINQ实现sql中类似left join左连的方法

    在Linq语句中实现SQL语句中类似left join的方法:左连接写法(from a in this.ObjectContext.T_SCHEDULE join b in this.ObjectContext.T_SPGROUP on a.SPGID equals b.ID into ab from c in ab.DefaultIfEmpty() //多个连接条件写法join d in this.ObjectContext.T_SCHED…

    2021/2/21 19:31:50
  • sql server中的Sum和Group by语法对应的LINQ语句如何写?

    SQL中的Sum和Group by语法对应的LINQ写法var q = from p in db.ReimbursementSub where (p.Reimbursement.State ==1) group p by new { p.Employee.CNName ,p.Project.ProjectName } into g select new { CNNa…

    2021/2/21 19:17:11
  • sql server中的in和not in语法对应的LINQ语句如何写?

    SQL中的in和not in语法对应的LINQ写法//sql查询语句:select * from product p where p.name not in(select f.name from tyre f) //Linq的写法:var a = (from p in product where !(from f in tyre select f.name).Contains(p.name) select p).ToList();

    2021/2/21 19:15:34