c# LINQ 到 object 子查询中的自增

Question

Good Afternoon? Could anyone suggest how I can implement autoincrement in linq to object subquery which must be started from 1 on every group of main linq query? I have query

from student in students
group student by student
into keyStudents
select new StudentClass
{
  Student = keyStudent.Key,
  Subjects = from key in keyStudent
            select new SubjectClass
            {
              Subject = key.Subject,
              SubjectId = (stuck here)
            }
}

My result must be like this:

Student
 John
   1. Math
   2. Bio
 Fred
   1. Math
   2. Physics
   3. Bio

My query returns accurate data without SubjectId, but I need to show SubjectId as well. So the SubjectId is just index number started with one in every group.

Answer 1

You'd have to use method syntax so you can use the override of Select that includes an index

from student in students
group student by student
into keyStudents
select new StudentClass
{
  Student = keyStudent.Key,
  Subjects = keyStudent.Select((x, i) =>
            new SubjectClass
            {
              Subject = x.Subject,
              SubjectId = i + 1,
            }),
}