Question

我是一名编程第一年的学生，我正在尝试制作抵押贷款计算器。用户输入他们的贷款金额和利率，选择15或30年的期限长度，并计算他们的每月付款。我认为数学是正确的，但我认为我遇到了转换数据类型的问题。我能够计算的唯一结果是＆＃34; Infinity＆＃34;。我也尝试将所有变量声明为双打，但没有区别。

以下是我遇到问题的代码段，并且完整代码中包含Option Strict On。任何提示将不胜感激！

    Dim decLoanAmount As Decimal
    Dim decInterestRate As Decimal
    Dim decFifteen As Decimal = 180D
    Dim decThirty As Decimal = 360D
    Dim decNumberOfMonths As Decimal
    Dim dblPayment As Double
    Dim decPayment As Decimal

    ' Did user enter a numeric value?

    If IsNumeric(txtLoanAmount.Text) And IsNumeric(txtInterestRate.Text) Then
        decLoanAmount = Convert.ToDecimal(txtLoanAmount.Text)
        decInterestRate = Convert.ToDecimal(txtInterestRate.Text)

        ' Is Loan Amount greater than zero?
        If decLoanAmount > 0 And decInterestRate > 0 Then
            If radFifteen.Checked = True Then
                decNumberOfMonths = decFifteen
            ElseIf radThirty.Checked = True Then
                decNumberOfMonths = decThirty
            End If

            ' Calculate the monthly payments as a double
            dblPayment = (decLoanAmount * (decInterestRate / 12 / 100) * (1 + (decInterestRate / 12 / 100) _
                ^ decNumberOfMonths)) / ((1 + (decInterestRate / 12 / 100) ^ decNumberOfMonths) - 1)
            ' Convert double to decimal
            decPayment = Convert.ToDecimal(decPayment)
            ' Display monthly payment
            lblPayment.Text = decPayment.ToString("C2")

        Else
            If decLoanAmount < 0 Then
                MsgBox("Please enter a valid loan amount.", , "Input error")
            End If

            If decInterestRate < 0 Then
                MsgBox("Please enter a valid interest rate.", , "Input error")
            End If

        End If

    Else
        ' Display error message if user entered a negative value.
        MsgBox("Please enter a numeric value.", , "Input Error")
    End If
End Sub

Answer 1

根据Wikipedia formula，您无法正确执行此操作。看起来应该是这样的：

dblPayment = (decLoanAmount * (decInterestRate / (12 * 100))) / (1 - (1 + (decInterestRate / (12 * 100))) ^ (-decNumberOfMonths))

此外，这条线很奇怪

decPayment = Convert.ToDecimal(decPayment)

应该是

decPayment = Convert.ToDecimal(dblPayment)

在Visual Basic中计算抵押贷款支付计算结果“无限”

1 个答案: