System.NullReferenceException: переменная объекта или переменная блока не установлены. VB.net

Question

Мне было поручено преобразовать сценарий Excel VBA в отдельное приложение Windows для VB.net. Я никогда раньше не пользовался VB.net и не могу решить эту проблему. Я заранее прошу прощения, если мой код является катастрофой, так как я узнаю, как VB.net работает на ходу.

MainForm.vb

Public Partial Class MainForm

Dim Sessions As Object
Dim System As Object
Dim Sess0 As Object
Dim oldSystemTimeout&
Dim g_HostSettleTime As Double

Public Sub New()
    Me.InitializeComponent()
End Sub

Public Sub costs_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles costs_box.TextChanged, other_box.TextChanged, poc_box.TextChanged
    Dim total As Double
    Dim costs As Double
    Dim other As Double
    Dim poc As Double
    costs = Val(costs_box.Text)
    other = Val(other_box.Text)
    poc = Val(poc_box.Text)
    total = costs + other + poc
    totalCosts_box.Text = total.ToString("C2")
End Sub

Public Sub seller_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles sellerLump_box.TextChanged, sellerSpecific_box.TextChanged
    Dim total As Double
    Dim lump As Double
    Dim specific As Double
    lump = Val(sellerLump_box.Text)
    specific = Val(sellerSpecific_box.Text)
    total = lump + specific
    totalSeller_box.Text = total.ToString("C2")
End Sub

Public Sub credits_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles sellerLump_box.TextChanged, sellerSpecific_box.TextChanged, dbCredit_box.TextChanged, lenderCredit_box.TextChanged
    Dim total As Double
    Dim lump As Double
    Dim specific As Double
    Dim db As Double
    Dim lender As Double
    lump = Val(sellerLump_box.Text)
    specific = Val(sellerSpecific_box.Text)
    db = Val(dbCredit_box.Text)
    lender = Val(lenderCredit_box.Text)
    total = lump + specific + db + lender
    totalCredits_box.Text = total.ToString("C2")
End Sub

Public Sub Clear_buttonClick(sender As Object, e As EventArgs)
    loanNumber_box.Clear
    costs_box.Clear
    other_box.Clear
    poc_box.Clear
    sellerLump_box.Clear
    sellerSpecific_box.Clear
    dbCredit_box.Clear
    lenderCredit_box.Clear
    loanType_box.Text = ""
    loanFamily_box.Text = ""
    propertyType_box.Text = ""
    salesPrice_box.Text = ""
    appValue_box.Text = ""
    cltv_box.Text = ""
    contribLimit_box.Text = ""
    decisionUpper_box.Text = ""
    decisionLower_box.Text = ""
    salesPrice_box.ForeColor = SystemColors.ControlText
    appValue_box.ForeColor = SystemColors.ControlText
    decisionUpper_box.ForeColor = SystemColors.ControlText
    decisionLower_box.ForeColor = SystemColors.ControlText
End Sub

Public Sub Run_buttonClick(sender As Object, e As EventArgs)
    LPS()
End Sub

Public Sub LPS()
'--------------------------------------------------------------------------------
' Get the main system object
    System = CreateObject("EXTRA.System") ' Gets the system object
    If (System Is Nothing) Then
        MsgBox ("Please open an NTS session")
        Exit Sub
    End If
    Sessions = System.Sessions

    If (Sessions Is Nothing) Then
        MsgBox ("Please open an NTS session")
        Exit Sub
    End If
'--------------------------------------------------------------------------------
' Set the default wait timeout value
    g_HostSettleTime = 50 ' Milliseconds Change As Needed. If retailChoice = 0 Then g_HostSettleTime = 150

    oldSystemTimeout& = System.TimeoutValue
    If (g_HostSettleTime > oldSystemTimeout) Then
        System.TimeoutValue = g_HostSettleTime
    End If

' Get the necessary Session Object
    Sess0 = System.ActiveSession
    If (Sess0 Is Nothing) Then
        MsgBox("Please open an NTS session")
        Exit Sub
    End If
    If Not Sess0.Visible Then Sess0.Visible = True
    Sess0.screen.WaitHostQuiet (g_HostSettleTime)

' Do not edit code above this line.

' Place your code here:
    Dim loanNumber As String
    Dim loanType As String
    Dim loanFamily As String
    Dim salesPrice As Double
    Dim appraisedValue As Double
    Dim propertyType As String
    Dim cltv As String
    Dim adjustedCLTV As Double
    Dim limit As Double
    Dim familyCounter As Integer
    Dim propertyCounter As Integer
    Dim priceCounter As Integer
    Dim contribLimit As Double
    Dim totalCredits As Double
    Dim totalCosts As Double
    loanNumber = loanNumber_box.Text
    If loanNumber = "" Then
        MsgBox("Please enter valid loan number", vbOKOnly)
        loanNumber = ""
        Exit Sub
    Else
        'LPS
        If Mid(loanNumber, 1, 2) = "02" Or Mid(loanNumber, 1, 2) = "04" Then
            loanType_box.Text = ""
            loanFamily_box.Text = ""
            propertyType_box.Text = ""
            salesPrice_box.Text = ""
            appValue_box.Text = ""
            cltv_box.Text = ""
            contribLimit_box.Text = ""
            salesPrice_box.BackColor = SystemColors.Control
            appValue_box.BackColor = SystemColors.Control
            Sess0.screen.SendKeys ("<Reset><Clear>sign<Enter>61<Enter>")
            Sess0.screen.WaitHostQuiet (g_HostSettleTime)
            Sess0.screen.PutString ("POINTS", 1, 3)
            Sess0.screen.PutString (loanNumber, 1, 12)
            Sess0.screen.SendKeys ("<ENTER>")
            Sess0.screen.WaitHostQuiet (g_HostSettleTime)
            loanType = Sess0.screen.getstring(6, 48, 1)
            loanFamily = Sess0.screen.getstring(9, 23, 1)
            salesPrice = Val(Sess0.screen.getstring(8, 11, 10))
            appraisedValue = Val(Sess0.screen.getstring(8, 29, 10))
            propertyType = Sess0.screen.getstring(7, 6, 4)
            cltv = Sess0.screen.getstring(9, 73, 6)
            adjustedCLTV = cltv / 100
            totalCredits = totalCredits_box.Text
            totalCosts = totalCosts_box.Text

            If loanType = "C" Then
                loanType_box.Text = "Conventional"

                If loanFamily = "C" Then
                    loanFamily_box.Text = "Conforming"
                    familyCounter = 1
                ElseIf loanFamily = "N" Then
                    loanFamily_box.Text = "Non-conforming"
                    familyCounter = 2
                End If

                If propertyType = "PRIM" Then
                    propertyType_box.Text = "Primary"
                    propertyCounter = 1
                ElseIf propertyType = "SECN" Then
                    propertyType_box.Text = "Secondary"
                    propertyCounter = 2
                ElseIf propertyType = "INVR" Then
                    propertyType_box.Text = "Investment"
                    propertyCounter = 3
                End If

                salesPrice_box.Text = salesPrice.ToString("C2")
                appValue_box.Text = appraisedValue.ToString("C2")
                If salesPrice < appraisedValue Then
                    priceCounter = 1
                    salesPrice_box.ForeColor = Color.ForestGreen
                ElseIf salesPrice > appraisedValue Then
                    priceCounter = 2
                    appValue_box.ForeColor = Color.ForestGreen
                ElseIf salesPrice = appraisedValue Then
                    priceCounter = 1
                    salesPrice_box.ForeColor = Color.ForestGreen
                    appValue_box.ForeColor = Color.ForestGreen
                End If

                cltv_box.Text = adjustedCLTV.ToString("P2")

            ElseIf loanType <> "C" Then
                MsgBox("Loan " & loanNumber & " is not a conventional loan", vbOKOnly)
                Exit Sub
            End If

            If familyCounter = 1 Then
                If propertyCounter = 1 Or propertyCounter = 2 Then
                    If cltv > 90# Then
                        limit = 0.03
                    ElseIf cltv > 75# And cltv <= 90# Then
                        limit = 0.06
                    ElseIf cltv <= 75# Then
                        limit = 0.09
                    End If
                ElseIf propertyCounter = 3 Then
                    limit = 0.02
                End If
            ElseIf familyCounter = 2 Then
                If propertyCounter = 1 Or propertyCounter = 2 Then
                    If cltv > 80# Then
                        limit = 0.03
                    ElseIf cltv <= 80# Then
                        limit = 0.06
                    End If
                ElseIf propertyCounter = 3 Then
                    limit = 0
                End If
            End If

            If priceCounter = 1 Then
                contribLimit = salesPrice * limit
            ElseIf priceCounter = 2 Then
                contribLimit = appraisedValue * limit
            End If

            contribLimit_box.Text = contribLimit.ToString("C2")

            If totalCredits > contribLimit And Not totalCredits > totalCosts Then
                decisionUpper_box.Font = New Font(decisionUpper_box.Font, FontStyle.Regular)
                decisionUpper_box.Text = "Total credits exceed contribution limit"
            ElseIf totalCredits > totalCosts And Not totalCredits > contribLimit Then
                decisionUpper_box.Text = "TOTAL CREDITS EXCEED TOTAL COSTS"
                decisionUpper_box.ForeColor = Color.Red
                decisionUpper_box.Font = New Font(decisionUpper_box.Font, FontStyle.Bold)
            ElseIf totalCredits > totalCosts And totalCredits > contribLimit Then
                decisionUpper_box.ForeColor = Color.Red
                decisionUpper_box.Font = New Font(decisionUpper_box.Font, FontStyle.Bold)
                decisionUpper_box.Text = "TOTAL CREDITS EXCEED TOTAL COSTS"
                decisionLower_box.Text = "Total credits exceed contribution limit"
                decisionLower_box.Font = New Font(decisionUpper_box.Font, FontStyle.Regular)
            ElseIf totalCredits < contribLimit Or totalCredits = contribLimit Then
                decisionUpper_box.Text = "PASS"
                decisionUpper_box.ForeColor = Color.Green
                decisionUpper_box.Font = New Font(decisionUpper_box.Font, FontStyle.Bold)
            End If
        End If
    End If
' Do not edit code below this line.

    System.TimeoutValue = oldSystemTimeout
    Sessions = Nothing
    System = Nothing
    Sess0 = Nothing
End Sub
End Class

Program.vb

Imports Microsoft.VisualBasic.ApplicationServices

Namespace My
    ' This file controls the behaviour of the application.
    Partial Class MyApplication
        Public Sub New()
            MyBase.New(AuthenticationMode.Windows)
            Me.IsSingleInstance = False
            Me.EnableVisualStyles = True
            Me.SaveMySettingsOnExit = False
            Me.ShutDownStyle = ShutdownMode.AfterMainFormCloses
        End Sub

        Protected Overrides Sub OnCreateMainForm()
            Me.MainForm = My.Forms.MainForm
        End Sub
    End Class
End Namespace

То, что я пытаюсь сделать, это создать переменные на уровне класса, которые доступны для всех моих функций / подпрограмм. Когда я компилирую приведенный ниже код и запускаю его, я получаю "System.NullReferenceException: переменная объекта или переменная блока не установлена". ошибка. Отладчик выделяет "Me.MainForm = My.Forms.MainForm" в Program.vb в качестве источника ошибки, но я не уверен, как ее исправить. Кто-нибудь может дать мне несколько советов в правильном направлении? Спасибо!

Answer 1

Я не уверен, что это все, что не так, но:

Dim System As Object

Это вызовет все виды проблем. В.NET уже есть пространство имен системы, и оно довольно важно, как вы можете увидеть всего несколькими строками позже:

Public Sub costs_TextChanged(ByVal sender As System.Object, ...

Переименуйте это:

Dim XSys as Object

путь внизу:

' Get the main system object
XSys = CreateObject("EXTRA.System") ' Gets the system object
If (XSys Is Nothing) Then
    MsgBox ("Please open an NTS session")
    Exit Sub
End If
Sessions = XSys.Sessions

If (Sessions Is Nothing) Then
    MsgBox ("Please open an NTS session")
    Exit Sub
End If

' at the very end:

XSys.TimeoutValue = oldSystemTimeout
Sessions = Nothing
XSys = Nothing

Это все еще может не работать, но наверняка, это не может работать так, как было