VB. NET: LINQ to SQL equivalent to Count - group by query - vb.net

Question

I'am trying to convert this query (already working):
Select building.Name, Count(people.ID) as NumberOfUser
From tblBuilding as building left outer join tblPeople as people on building.ID = people.buildingID
Group by building.Name
which gave the result like this:
Name | NumberOfUser
----------------------------
WestBuilding 50
EastBuilding 70
SouthBuilding 0
NorthBuilding 2
To Linq to SQL. Look at my trying:
Dim db As New MyDatabaseDataContext
Dim query = From building In db.tblBuilding
From people In db.tblPeople.Where(Function(x) building.ID = x.buildingID).DefaultIfEmpty
Group building, people By building.ID, building.Name Into grp
Select ID, Name, grp.Count
Return query.ToList
It appeared to work at first. But when I checked a building that contained no people, the Count column said there is 1. Like this:
Name | NumberOfUser
----------------------------
WestBuilding 50
EastBuilding 70
SouthBuilding 1
NorthBuilding 2
Because although that building had no people, it did appeared once in the result query so it counted as 1. In another word, the Count statement actually count how many time each building appear in result table instead of how many people in each building, thus making the result wrong for no people building.
Any work around ?

Answer 1

You are correct, to solve it you need to test whether there are people, like you did with count(people.Id)
Dim db As New MyDatabaseDataContext
Dim query = From building In db.tblBuilding
From people In db.tblPeople.Where(Function(x) building.ID = x.buildingID).DefaultIfEmpty
Group building, people By building.ID, building.Name Into Group, Count(Not IsNothing(people))
'Select ID, Name, grp.Count
Return query.ToList