For..Next，是否退出无法正常工作? [英] For..Next, Exit For Not Working as Expected?

问题描述

当学生登录时，我为他们加载了一个仪表板，以让他们了解他们在住房预订过程中所处的位置.不管我做什么，即使我在For..Next循环中都有Exit For，它似乎总是会触发Else条件.这是有问题的代码:

When a student logs in I load a dashboard for them giving them an idea of where they are at in the housing reservation process. No matter what I do though it always seems to trigger the Else condition, even though I have an Exit For in the For..Next loop. Here is the code in question:

Public Sub Initialize_Dashboard()
    Dim term As String = CStr(Session("term"))
    Dim year As String = CStr(Session("year"))
    Dim people_code_id As String = CStr(Session("people_code_id"))
    Dim class_level As String = CStr(Session("class"))
    ' %%%%%% Show the resident's name and whether they have a room. %%%%%%
    Dim dbroom As New pbu_housingEntities
    Dim queryStudent = From p In dbroom.Residents _
                       Where p.people_code_id = people_code_id _
                       Join b In dbroom.Buildings On p.building Equals b.id _
                       Join r In dbroom.Rooms On p.room Equals r.id
                       Select p, b, r

    lblName.Text = CStr(Session("name"))
    If queryStudent.Count.Equals(0) Then
        lblRegistered.Text = "We do not have you currently registered for campus housing."
    Else
        lblRegistered.Text = "You are currently registered for " & queryStudent.First.b.building_name & " " & queryStudent.First.r.room1 & "."
    End If

    ' Initiate variables to check for class settings.
    Dim dbConfig As New pbu_housingEntities
    Dim whatdatest = From p In dbConfig.Configs
    Dim whatdatee = From p In dbConfig.Configs

    ' Add in a check for contract signatures.
    Dim dbContracts As New pbu_housingEntities
    Dim clcexists = From p In dbContracts.Signatures _
                    Where p.StudentID = people_code_id _
                    And p.ContractType = "clc" _
                    Order By p.ID Descending _
                    Select p
    Dim rhcexists = From p In dbContracts.Signatures _
                    Where p.StudentID = people_code_id _
                    And p.ContractType = "rhc" _
                    Order By p.ID Descending _
                    Select p
    ' Shows or hides the buttons for contracts based on whether signatures exist.
    Dim clcfirst = clcexists.FirstOrDefault()
    Dim rhcfirst = rhcexists.FirstOrDefault()
    If clcfirst Is Nothing Then
        pnlSignCLC.Visible = True
    Else
        pnlSignCLC.Visible = False
    End If
    If rhcfirst Is Nothing Then
        pnlSignRHC.Visible = True
    Else
        pnlSignRHC.Visible = False
    End If

    ' Determine if the student is eligible to register for class.
    Dim classes() As String = {"FR%", "SO", "JR", "SR", "SR5"}
    For Each value As String In classes
        ' Pull in the dates the student should be able to register for this class, compare them to the current date.
        Dim current_value = value
        If class_level = current_value Then
            Response.Write("hello")
            whatdatest = From p In dbConfig.Configs _
                         Where p.Description = current_value + "OD" _
                         Select p

            whatdatee = From p In dbConfig.Configs _
                        Where p.Description = current_value + "CD" _
                        Select p

            ' If the current date is within their registration period...
            If Date.Now >= whatdatest.First.dateValue And Date.Now <= whatdatee.First.dateValue Then
                Dim person_name As String = CStr(Session("person_name")) ' Must stay here or will conflict.
                Dim hasroom = From p In dbConfig.Residents _
                              Where p.person_name = person_name _
                              Where p.semester = term _
                              Where p.year = year _
                              Select p
                ' If they have signed their contracts, lets let them register for a room.
                If hasroom.Count.Equals(0) AndAlso clcfirst IsNot Nothing AndAlso rhcfirst IsNot Nothing Then
                    pnlBegin.Visible = True
                    btnBegin.Enabled = True

                    ' If they are already registered for a room, let them delete their reservation.
                ElseIf clcfirst IsNot Nothing AndAlso rhcfirst IsNot Nothing Then
                    pnlDelete.Visible = True
                    btnDelete.Enabled = True
                Else

                    ' In any other situation, we don't need to do anything.
                    ' There really shouldn't be any other situation.

                End If
                ' What to do if the current date is not within the room reservation window.
                Exit For
            Else
                Dim class_name As String
                Select Case current_value
                    Case "FR%"
                        class_name = "Freshman"
                    Case "SO"
                        class_name = "Sophmore"
                    Case "JR"
                        class_name = "Junior"
                    Case "SR"
                        class_name = "Senior"
                    Case "SR5"
                        class_name = "Fifth year Senior"
                End Select
                lblError.Text = "You are currently a " & current_value & ". You will be eligible to reserve a room between" _
                    & whatdatest.First.dateValue & " and " & whatdatee.First.dateValue & ". Please come back during those dates. Thanks!"
            End If
            Exit For
        Else
            ' What to do if the user isn't assigned a class level at all!
            lblError.Text = "Oops...Something might be wrong with our records. We don't have you registered for classes. Please contact Dave Mackey, x4543."
        End If
    Next

这是我将最后一个else子句移至单独的If..Then之后的代码:

Here is the code after I moved the last else clause into a separate If..Then:

 Public Sub Initialize_Dashboard()
    Dim term As String = CStr(Session("term"))
    Dim year As String = CStr(Session("year"))
    Dim people_code_id As String = CStr(Session("people_code_id"))
    Dim class_level As String = CStr(Session("class"))
    ' %%%%%% Show the resident's name and whether they have a room. %%%%%%
    Dim dbroom As New pbu_housingEntities
    Dim queryStudent = From p In dbroom.Residents _
                       Where p.people_code_id = people_code_id _
                       Join b In dbroom.Buildings On p.building Equals b.id _
                       Join r In dbroom.Rooms On p.room Equals r.id
                       Select p, b, r

    lblName.Text = CStr(Session("name"))
    If queryStudent.Count.Equals(0) Then
        lblRegistered.Text = "We do not have you currently registered for campus housing."
    Else
        lblRegistered.Text = "You are currently registered for " & queryStudent.First.b.building_name & " " & queryStudent.First.r.room1 & "."
    End If

    ' Initiate variables to check for class settings.
    Dim dbConfig As New pbu_housingEntities
    Dim whatdatest = From p In dbConfig.Configs
    Dim whatdatee = From p In dbConfig.Configs

    ' Add in a check for contract signatures.
    Dim dbContracts As New pbu_housingEntities
    Dim clcexists = From p In dbContracts.Signatures _
                    Where p.StudentID = people_code_id _
                    And p.ContractType = "clc" _
                    Order By p.ID Descending _
                    Select p
    Dim rhcexists = From p In dbContracts.Signatures _
                    Where p.StudentID = people_code_id _
                    And p.ContractType = "rhc" _
                    Order By p.ID Descending _
                    Select p
    ' Shows or hides the buttons for contracts based on whether signatures exist.
    Dim clcfirst = clcexists.FirstOrDefault()
    Dim rhcfirst = rhcexists.FirstOrDefault()
    If clcfirst Is Nothing Then
        pnlSignCLC.Visible = True
    Else
        pnlSignCLC.Visible = False
    End If
    If rhcfirst Is Nothing Then
        pnlSignRHC.Visible = True
    Else
        pnlSignRHC.Visible = False
    End If

    ' Determine if the student is eligible to register for class.
    Dim classes() As String = {"FR%", "SO", "JR", "SR", "SR5"}
    Dim flag As String = "N"
    For Each value As String In classes
        ' Pull in the dates the student should be able to register for this class, compare them to the current date.
        Dim current_value = value
        If class_level = current_value Then
            flag = "Y"
            Response.Write("hello")
            whatdatest = From p In dbConfig.Configs _
                         Where p.Description = current_value + "OD" _
                         Select p

            whatdatee = From p In dbConfig.Configs _
                        Where p.Description = current_value + "CD" _
                        Select p

            ' If the current date is within their registration period...
            If Date.Now >= whatdatest.First.dateValue And Date.Now <= whatdatee.First.dateValue Then
                Dim person_name As String = CStr(Session("person_name")) ' Must stay here or will conflict.
                Dim hasroom = From p In dbConfig.Residents _
                              Where p.person_name = person_name _
                              Where p.semester = term _
                              Where p.year = year _
                              Select p
                ' If they have signed their contracts, lets let them register for a room.
                If hasroom.Count.Equals(0) AndAlso clcfirst IsNot Nothing AndAlso rhcfirst IsNot Nothing Then
                    pnlBegin.Visible = True
                    btnBegin.Enabled = True

                    ' If they are already registered for a room, let them delete their reservation.
                ElseIf clcfirst IsNot Nothing AndAlso rhcfirst IsNot Nothing Then
                    pnlDelete.Visible = True
                    btnDelete.Enabled = True
                Else

                    ' In any other situation, we don't need to do anything.
                    ' There really shouldn't be any other situation.

                End If
                ' What to do if the current date is not within the room reservation window.
                Exit For
            Else
                Dim class_name As String
                Select Case current_value
                    Case "FR%"
                        class_name = "Freshman"
                    Case "SO"
                        class_name = "Sophmore"
                    Case "JR"
                        class_name = "Junior"
                    Case "SR"
                        class_name = "Senior"
                    Case "SR5"
                        class_name = "Fifth year Senior"
                End Select
                lblError.Text = "You are currently a " & current_value & ". You will be eligible to reserve a room between" _
                    & whatdatest.First.dateValue & " and " & whatdatee.First.dateValue & ". Please come back during those dates. Thanks!"
            End If
            Exit For
        Else

        End If
    Next
    If flag = "N" Then
        ' What to do if the user isn't assigned a class level at all!
        lblError.Text = "Oops...Something might be wrong with our records. We don't have you registered for classes. Please contact Dave Mackey, x4543."
    End If

推荐答案

我认为您需要删除最后一条Else语句

I think you need to remove this last Else statement

Else
            ' What to do if the user isn't assigned a class level at all!
            lblError.Text = "Oops...Something might be wrong with our records. We don't have you registered for classes. Please contact Dave Mackey, x4543."

否则，您将永远无法通过所有选项.

Otherwise you will never get through all the options.

您需要在循环之前将"found"标志设置为false，如果有匹配项，则在循环内部将found设置为true，然后在循环之后将发现的错误设置为false.

You need to set a "found" flag to false before the loop, set found to true inside the loop if there is a match, then after the loop set the error if found is still false.

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