Error - Method 'First' Can Only Be Used As A Final Query Operation

I have the following query:

Dim roommates = From p In dbroom.Residents _
Where p.room = queryStudent.First.r.id _
Where p.building = queryStudent.First.b.id _
Where p.year = year _
Where p.semester = term _
Select p.person_name

It currently returns no results. I was getting an error when attempting to bind this resultset (since it was empty) to a repeater in ASP.NET, so I attempted to escape it:

If roommates.Count() = 0 Then
Dim nomates As String = "No current roommates."
rptrRoommates.DataSource = nomates
rptrRoommates.DataBind()
Else
rptrRoommates.DataSource = roommates
rptrRoommates.DataBind()
End If

But I still get the same error:

The method 'First' can only be used as a final query operation. Consider using the method 'FirstOrDefault' in this instance instead.