LINQ group results - entity-framework

Question

I've spent the whole day trying to figure out how to JOIN / group my query below, can someone help me or guide me to complete the desired output? -i enclosed some of the foreign key values for easy reference)
Below is my Table Grade
rowID testID studentID Grade
1 1 1(class2011) 50
2 1 1(class2011) 90
3 2 1(class2011) 100
4 2 2(class2012) 85
--Student table
StudentID Classyear
1 2(class2011)
2 3(class2012)
3 1(class2010)
--Classyear Table
ClassYearID Desc
1 2010
2 2011
3 2012
My query below (to display the testID, failed(passing rate=80), passed, taken, Rate)
var h = list.GroupBy(a => a.testID)
.Select(a => {
int _failed = a.Count(g => g.Grade < 80);
int _passed = a.Count(g => g.Grade >= 80);
int _rate = (int)(_passed / (double)a.Count() * 100.0);
return new {
testID = a.Key,
failed = _failed,
passed = _passed,
taken = a.Count(),
rate = _rate,
};
});
The result1
testID failed passed taken Rate
1 1 1 2 50%
2 0 2 2 100%
Now here's my BIG problem: the students in my table grade above DOES NOT belong in the
same classyear. I need to group this by testID and classyear.
See below for the desired output:
testID ClassyearID failed passed taken Rate
1 1(2010) 0 0 0 0
1 2(2011) 1 1 2 50%
1 3(2012) 0 0 0 0
2 1(2010) 0 0 0 0
2 2(2011) 0 1 1 100%
2 3(2012) 0 1 1 100%
You can immediately see the difference from result 1. stats for Test2 is divided for class 2011 and class 2012.
Hope I did explain clear enough my intentions. Maybe I will post later my crappy code trying to get the desired output. Thanks

Answer 1

Can't you just do this?:
var h = list.GroupBy(a =>new {a.testID,a.classyear})
.Select(a => {
int _failed = a.Count(g => g.Grade < 80);
int _passed = a.Count(g => g.Grade >= 80);
int _rate = (int)(_passed / (double)a.Count() * 100.0);
return new {
testID = a.Key.testID,
classyear=a.Key.classyear,
failed = _failed,
passed = _passed,
taken = a.Count(),
rate = _rate,
};
});