LINQ - join with Group By and get average

SQL:

SELECT DeptId,avg(Marks) FROM StudentTb s
JOIN StudInDepartment d on s.StudentId = 开发者_StackOverflowd.StudentId
GROUP BY DeptId

Convert into Linq:

  var deptRpts =         from s in this.ObjectContext.StudentTb
                         join d in this.ObjectContext.StudInDepartment on s.StudentId equals d.StudentId  
                         group s by d.DeptId into grp
                         select new {
                             DeptId = grp.Key,
                             AverageMarks = grp.Average(ed=>ed.Marks)
                         };

Got an empty result list.

While expanding the result-set in debug mode.Its shows error function evaluation timed out

Need help on this.

The query works fine as is, at least in my mock up I just threw together ... it may have something to do with how the database is structured....in my mock up I have the studentID as a foreign key to the StudInDepartment (ha!) table and even this simplified query works ok

var deptRpt2 = from d in ctx.StudInDepartment
   group d by d.DeptId into grp
   select new {
      Dept = grp.Key,
      AverageMarks = grp.Average(ed=>ed.StudentTb.Marks)
   };

The message you received "function evaluation timed out" may be the Visual Studio debugger issue, can't help you there, theres other threads off stackoverflow that discuss it as well.