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我有以下查詢:實體框架導航屬性未設置爲對象的實例?
Dim queryStudent = (From p In dbContext.Residents _
Where p.people_code_id = people_id _
Where p.year = year _
Where p.semester = semester _
Join b In dbContext.Buildings On p.building Equals b.id _
Join r In dbContext.Rooms On p.room Equals r.id
Select p, b, r)
我然後嘗試拉大樓和客房爲個人,像這樣:
room = queryStudent.FirstOrDefault.r.id
building = queryStudent.FirstOrDefault.b.id
但是我收到一個Object reference not set to an instance of an object
錯誤。
我試着做一些像
If IsNothing(queryStudent.FirstOrDefault.r.id) Then
room = ""
Else
room = queryStudent.FirstOrDefault.r.id
End If
但仍然產生了同樣的錯誤。