在實體框架中將SQL轉換為Linq查詢

Question

如何在實體框架中將此查詢轉換為LINQ查詢？ 我是還在上學的新程序員

SELECT 
    studfirstname, studlastname, grade
FROM 
    students
INNER JOIN 
    Student_Schedules ON students.StudentID = Student_Schedules.StudentID
INNER JOIN 
    Classes ON Student_Schedules.ClassID = Classes.ClassID
INNER JOIN 
    Subjects ON Classes.SubjectID = Subjects.SubjectID
WHERE 
    SubjectName = 'Introduction to Art';

Answer 1

正如你在Lambda和LINQ是新的我在下面LAMBDA試圖盡可能描述.....你可以使用長別名以簡短的形式也student_schedules作為ss或studentsANDstudent_schedules作為s_s_sch ......嘗試......希望這會有所幫助.... @Abdul Hameed

var filteredData = context.Students    // your starting point
   .Join(context.Student_Schedules, // the source table of the inner join
      students => students.StudentID,        // Select the primary key (the first part of the "on" clause in an sql "join" statement)
      student_schedules => student_schedules.StudentID),// the foreign key
      (students, student_schedules) => new { students, student_schedules })
   .Join(context.Classes,
      classes => classes.ClassID,        
      studentsANDstudent_schedules => studentsANDstudent_schedules.student_schedules.ClassID),
      (classes, studentsANDstudent_schedules) => new { classes, studentsANDstudent_schedules })
   .Join(context.Subjects,
      subjects => subjects.SubjectID,        
      studentsANDstudent_schedulesANDClasses => studentsANDstudent_schedulesANDClasses.classes.SubjectID),
      (subjects, studentsANDstudent_schedulesANDClasses) => new { subjects, studentsANDstudent_schedulesANDClasses })
   .Where(allMergedTables => allMergedTables.subjects.SubjectName == "Intoduction to Art").ToList();

這是以上版本的簡化版本...

var filteredData = context.Students 
   .Join(context.Student_Schedules, s => s.StudentID, sch => sch.StudentID),
      (s, sch) => new { s, sch })
   .Join(context.Classes, c => c.ClassID, s_sch => s_sch.sch.ClassID),
      (c, s_sch) => new { c, s_sch })
   .Join(context.Subjects, sj => sj.SubjectID, s_sch_c => s_sch_c.c.SubjectID), 
      (sj, s_sch_c) => new { sj, s_sch_c })
   .Where(all => all.sj.SubjectName == "Intoduction to Art")
   .ToList();

Answer 2

您可以使用LINQ語法：

from student in context.Students
join schedule in context.Student_Schedules on student.StudentID equals schedule.StudentID
join @class in context.Classes on schedule.ClassID equals @class.ClassID
join subject in context.Subjects on @class.SubjectID equals subject.SubjectID
where subject.SubjectName == "Introduction to Art"

Answer 3

var students = context.Students.Include("Student_Schedules")
                               .Include("Classes")
                               .Include("Subjects").Where(s => s.Subjects.Contains("Intoduction to Art"));

信息-> https://msdn.microsoft.com/zh-cn/data/jj574232.aspx