每次我离开并重新进入班级时，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。我应该打电话给一个班级来完成这项工作，然后将答案返回到表格中。然而，由于某种原因，每当我的程序移出类，返回表单，然后返回类时，我在类中的变量就会重置为 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

来自关联类的代码：

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

因此，每个对象都是 finClass 对象的

不同

实例。所以每次你“重新进入”类时，你实际上进入了该类对象的一个不同实例，这就是为什么所有变量的值= 0。它们还没有被实例化或设置。

尝试这样做，创建一个类对象，您可以使用类模块中的方法来操作它：

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

Answer 2

创建一个模块并使用“公共”来衡量变量 公共模块示例 公共示例变量作为整数 结束模块

这将允许变量在程序运行期间保留其值。在表单类中使用 dim 会导致每次加载表单时该值都会重新调整

Answer 3

您遇到的另一个问题是，当您的表单完成私有子例程时，它会将您的所有变量集作为 finclass 丢弃。这意味着当您再次按下时，它将重新开始为 0。您将需要在表单类中创建类的变量，这样当您回调它时就不会重置它。

公开课F_Form1 将 objFinClass 调暗为新 finClass Private Sub ButtonCalc_Click(sender As Object, e As EventArgs) 处理buttonCalc.Click

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

结束子 下课