使用LINQ从多个表中检索数据

Question

I'am beginner in linq and have three tables (sql ce 3.5) like this : course : (PK)CourseCode,CourseName Class : (PK)ClassCode,FieldCode,ClassName ClsCrs : (PK)ClassCode,(PK)CourseCode

I want to convert or rewrite this query to linq and assign results to a combobox data source :

`SELECT CourseName FROM class, clscrs, course WHERE
ClassTitel = @ClassTitel and class.classcode = clscrs.classcode and
clscrs.coursecode = course.coursecode`

how can i do this ?

thanks

Answer 1

you can try this

var query = (from c in db.class 
             from v in db.clscrs 
             from n in db.course 
             where c.ClassTitel=="yourinput" 
                 && c.classcode = v.classcode 
                 && v.coursecode = n.coursecode 
             select n.CourseName).ToList();

Answer 2

Its not clear which table ClassTitel field belongs (assume class table). Also replace set names with those generated by EF or Linq to SQL

var query = from cl in db.class
            join cc in db.clscrs on cl.classcode equals cc.classcode
            join cs in db.course on cc.coursecode equals cs.coursecode
            where cl.ClassTitel == "value"
            select cl.CourseName;

comboBox1.DataSource = query.ToList();