使用dbContexts变量不可用？

问题描述

| 我有以下代码，在使用dbPC的getOc​​cupants调用中引发错误。有没有一种方法可以在使用dbPC中使该值可访问？还是更好的方法来实现这一目标？我尝试在“使用dbContext”中嵌套“使用dbPC”，但这也会引发错误。

  Protected Sub btnPushSemester_Click(sender As Object,e As EventArgs) Handles btnPushSemester.Click
    Dim dbPC As New Campus6Entities
    Dim dbContext As New pbu_housingEntities
    Using dbContext
        Dim get_Year = From p In dbContext.Configs _
                           Where p.Description = \"year\" _
                           Select p

        Dim get_Term = From p In dbContext.Configs _
                       Where p.Description = \"term\" _
                       Select p

        Dim thisYear = get_Year.First.textValue
        Dim thisTerm = get_Term.First.textValue
        Dim getOccupants = From p In dbContext.Residents _
                 Where p.semester = thisTerm _
                 Where p.year = thisYear _
                 Select p
    End Using
    Using dbPC
        For Each row In getOccupants
            Dim student_info = row
            Dim PCstudent = From r In dbPC.RESIDENCies _
                            Where student_info.people_code_id = r.PEOPLE_ID _
                            Where r.ACADEMIC_YEAR = thisYear _
                            Where r.ACADEMIC_TERM = thisTerm _
                            Select r

            For Each row2 In PCstudent
                Dim student_info2 = row2
                student_info2.DORM_BUILDING = student_info.Building1.building_code
                student_info2.DORM_ROOM = student_info.Room1.room1
                student_info2.RESIDENT_COMMUTER = \"R\"
                student_info2.DORM_CAMPUS = \"O000000001\"
                dbPC.SaveChanges()
            Next
        Next
    End Using

End Sub

    

解决方法

        在using块外声明

getOccupants

。您可以在块内分配它，但是必须在外部声明它，否则它会超出范围，然后才真正需要使用它。     ,        由于执行延迟，因此直到您遍历集合之前，查询才真正执行，但是到那时，您已经处置了dbContext对象。尝试将所有代码包含在“使用”块中：

Using dbPC As New Campus6Entities
    Using dbContext As New pbu_housingEntities
        \'rest of code here
    End Using
End Using