Comparing Two Queries and Synchronizing Results - asp.net

Question

I have a table (Rooms) which contains a number of rows. Each row represents a room and each room needs to exist twice (once for fall, once for spring semester). Sometimes when folks add a room they only add it for one semester. I'm working on a process that will synchronize the rooms between semesters.
First I've pulled two queries, one that gets all of the rooms with fall in their semester column and one that gets all of the rooms with spring in their semester column, like so:
Dim getFallRooms = (From p In dbContext.Rooms _
Where p.semester = "Fall" _
Select p)
Dim getSpringRooms = (From p In dbContext.Rooms _
Where p.semester = "Spring" _
Select p)
The results will each contain multiple rows with the following columns: id, building, room, occupant, and semester.
What I want to do is something like this (pseudo):
For Each row in getFallRooms
If row.building and row.room not in getSpringRooms Then
' Code to add new row with fall as the semester.
End If
Next
Any suggestions on how I can make this into actual, workable code?

Answer 1

For Each row in getFallRooms
If (From p in getSpringRooms
Where p.building = row.building
AndAlso p.room = row.room).Count = 0 Then
' Code to add new row with fall as the semester.
End If
Next

Answer 2

You could do something quite similar to what's being done at this link.
I don't know precisely how to do it in VB.NET, but here's how I would do it in C#, using the LINQ extension methods:
var fallRooms = dbContext.Rooms.Where(room => room.semester.Equals("Fall")).Select(r => r.Name);
var nonSpringRooms = dbContext.Rooms.Where(room => room.semester.Equals("Spring"))
.Select(r => r.Name)
.AsQueryable()
.Except(fallRooms);
Afterwards, you could then do a For Each loop on nonSpringRooms to do whatever it is that you'd want to do.
On a side note, someone should correct me if I'm wrong, but I believe that the above code would only go to the database once. Hence, you'd get that benefit as well.
EDIT: I realized that since they'd be on the same table that the records would have the same primary key. I've subsequently changed the query above, assuming that you have a name field that would be the same in both records.