vb.net - 每次我离开并重新进入类时，Visual Basic 都会将我的变量重置为 0

Question

我有一个表格可以从用户那里获取财务信息，包括贷款金额、利率和期限。我应该调用一个类(class)来完成这项工作，然后将答案返回给表格。但是，出于某种原因，每当我的程序移出类，返回表单，然后返回类时，我在类中设置的变量都会重置为 0。我的代码如下。任何帮助都会很棒。

这是我表单中的代码:

    'Preform calculation when button is clicked
Private Sub buttonCalc_Click(sender As Object, e As EventArgs) Handles buttonCalc.Click
    Dim loanAmount As New finClass
    Dim rate As New finClass
    Dim term As New finClass
    Dim payment As New finClass
    loanAmount.getLoanAmount = textBoxMortgageAmount.Text
    rate.getAnnualRate = comboBoxAnnualRate.Text.Replace("%", "")
    term.getTermInYears = comboBoxTerm.SelectedItem
    textBoxMonthlyPayment.Text = payment.setMonthlyPayment

End Sub

关联类中的这段代码:

Public Class finClass

Private loanAmt As Decimal
Private termValue As Decimal
Private rateValue As Decimal
Public paymentValue As Decimal

Public WriteOnly Property getLoanAmount
    Set(value)
        If IsNumeric(value) AndAlso value > 1000 AndAlso value < 10000000 Then
            Me.loanAmt = value
        Else
            MessageBox.Show("Mortgage amount must be a number between $1,000 and $10,000,000", "Invalid Number", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End If
    End Set
End Property

Public WriteOnly Property getAnnualRate
    Set(value)
        rateValue = value.Replace("%", "")
        If rateValue < 1 Then
            rateValue *= 100
        End If

    End Set
End Property

Public WriteOnly Property getTermInYears
    Set(value)
        termValue = value
    End Set
End Property

Public ReadOnly Property setMonthlyPayment
    Get
        Return -Pmt((rateValue / 1200), termValue * 12, Me.loanAmt)
    End Get
End Property
End Class

Answer 1

我不在 VS 中工作，但看起来您正在创建该类的四个实例。我很确定这是不正确的。

Private Sub buttonCalc_Click(sender As Object, e As EventArgs) Handles buttonCalc.Click
    Dim loanAmount As New finClass  '## Creates NEW finClass object
    Dim rate As New finClass        '## Creates NEW finClass object
    Dim term As New finClass        '## Creates NEW finClass object
    Dim payment As New finClass     '## Creates NEW finClass object
    loanAmount.getLoanAmount = textBoxMortgageAmount.Text
    rate.getAnnualRate = comboBoxAnnualRate.Text.Replace("%", "")
    term.getTermInYears = comboBoxTerm.SelectedItem
    textBoxMonthlyPayment.Text = payment.setMonthlyPayment

End Sub

所以这些对象中的每一个都是 finClass 对象的不同实例。因此，每次您“重新进入”该类时，您实际上是在进入该类对象的不同实例，这就是为什么所有变量的值都为 0 的原因。它们尚未被实例化或设置, 然而。

试试这个，创建一个你用类模块中的方法操作的类对象:

Private Sub buttonCalc_Click(sender As Object, e As EventArgs) Handles buttonCalc.Click
    Dim objFinClass as New finClass

    objFinClass.getLoanAmount = textBoxMortgageAmount.Text
    objFinClass.getAnnualRate = comboBoxAnnualRate.Text.Replace("%", "")
    objFinClass.getTermInYears = comboBoxTerm.SelectedItem
    textBoxMonthlyPayment.Text = objFinClass.setMonthlyPayment

End Sub