LINQ嵌套查询

墨_yan 2013-10-11 09:42:09

public ActionResult Show()
{
IEnumerable<Show> model = from o in _db.CourseOrder.ToList<CourseOrder>()
select new Show
{
Classname = from s in _db.Classes where s.Classno == o.Classno select s.Classname ,
UseTime = o.UseTime,
Roomno = o.Roomno,
Cname = from p in _db.Courses where p.Cno == o.Cno select p.Cname,
Tname = from q in _db.Teachers where q.Tno == o.Tno select q.Tname
};
return View(model);
}
怎么实现LINQ嵌套查询啊？这些语句怎么都实现不了？Classname = from s in _db.Classes where s.Classno == o.Classno select s.Classname ,
Cname = from p in _db.Courses where p.Cno == o.Cno select p.Cname,
Tname = from q in _db.Teachers where q.Tno == o.Tno select q.Tname
纠结好久了，求了解的人帮帮忙，谢谢

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u011055410 2014-03-19

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做个记号；；；；

墨_yan 2013-10-12

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引用 2 楼 q107770540 的回复:

不过我建议你用inner join:

IEnumerable<Show> model = from  o in _db.CourseOrder 
                            join s in _db.Classes on o.Classno equals s.Classno
                            join p in _db.Courses on o.Cno equals p.Cno
                            join q in _db.Teachers on o.Tno equals q.Tno
                            select new Show
                                {
                                     Classname =s.Classname ,   
                                     UseTime = o.UseTime,
                                     Roomno = o.Roomno,
                                     Cname =p.Cname, 
                                     Tname =q.Tname   
                                 }

首先真的特别谢谢您，还有我想问您一下，关于学习LINQ，你能给推荐一本书或者可以用来学习的资料或网站吗？我刚接触，什么都不懂，谢谢!

q107770540 2013-10-12

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http://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b

u010316723 2013-10-12

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还真不看得出

threenewbee 2013-10-12

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其实Linq很简答。它就是一组函数调用。建构在泛型、委托、Lambda表达式、接口这几个概念上，如果你能把这几个概念搞清楚，Linq就很容易理解，根本不要怎么学了。

q107770540 2013-10-11

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不过我建议你用inner join:

IEnumerable<Show> model = from  o in _db.CourseOrder 
                            join s in _db.Classes on o.Classno equals s.Classno
                            join p in _db.Courses on o.Cno equals p.Cno
                            join q in _db.Teachers on o.Tno equals q.Tno
                            select new Show
                                {
                                     Classname =s.Classname ,   
                                     UseTime = o.UseTime,
                                     Roomno = o.Roomno,
                                     Cname =p.Cname, 
                                     Tname =q.Tname   
                                 }

q107770540 2013-10-11

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 IEnumerable<Show> model = from  o in _db.CourseOrder 

                           select new Show

                           {

                               Classname = _db.Classes.Single(s=> s.Classno == o.Classno).Classname ,   

                               UseTime = o.UseTime,

                               Roomno = o.Roomno,

                               Cname =_db.Courses.Single(p=> p.Cno == o.Cno).Cname, 

                               Tname =_db.Teachers.Single(q=>q.Tno == o.Tno).Tname