Question

有人可以帮我把这个SQL转换成linq或lambda c＃

select  
    count(s.ClassId) [StudentInClass], c.Name [Class], t.Name [teacher]
from 
    [dbo].[Students] s
inner join 
    class c on s.ClassId = c.Id
inner join Teacher t 
    on t.Id = c.TeacherId
group by 
    s.ClassId, c.Name, t.Name

到目前为止，这就是我所拥有的，而且我搞砸了。我希望获得与我的SQL查询相同的结果

        SchoolEntities db = new SchoolEntities();

        var StudentsByCourseId = from s in db.Students
            join c in db.Classes on s.ClassId equals c.Id
            join t in db.Teachers on c.TeacherId equals t.Id
            group c by s.ClassId
            into g
            select g;

在SQL中，这就是我的结果，它是老师在课堂上对学生进行计数的重要因素

 
          StudentCount  Class        Teacher
          1             Geography    Teacher1
          1             Biology      Teacher1
          2             Maths        Teacher2

Answer 1

您可以使用匿名类按多个属性进行分组。

 var StudentsByCourseId = from s in db.Students
            join c in db.Classes on s.ClassId equals c.Id
            join t in db.Teachers on c.TeacherId equals t.Id
            group s by new { s.ClassId, Class = c.Name, Teacher = t.Name } 
            into g
            select new
            {
              StudentInClass = g.Count(),
              g.Key.Class,
              g.Key.Teacher,
            };

将其转换为linq或lambda c＃

1 个答案: