由于Visual Basic中的按揭付款计算中收到“infinity”

我是第一年的编程学生，正在努力制作按揭付款计算器。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，他们的每月付款应计算。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“无限”。我也试着将所有变量声明为双精度，但没有区别。由于Visual Basic中的按揭付款计算中收到“infinity”

下面是我遇到的一段代码，Option Strict On包含在完整的代码中。任何提示将非常感谢！

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

来源

2014-12-07 SJW

我建议保理出来了一下，检查值就像你所期望的那样 - 例如，在计算过程中会重复'（decInterestRate/12/100）'，所以为什么不先计算它，然后检查这个值是否如你所期望的那样。 – 2014-12-07 21:08:49

此外，'decPayment = Convert.ToDecimal（decPayment）'不会做很多... – 2014-12-07 21:09:59

您不希望人们在这里为您编写和/或调试代码，对吧？向我们展示一些研究，提供样本输入，输出，更多解释。假设上面的代码不在那里，你认为你描述的内容足以帮助你吗？ – Neolisk 2014-12-07 21:48:08

根据Wikipedia formula，您的操作不正确。它应该是这个样子：

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

而且，这条线是怪异

decPayment = Convert.ToDecimal(decPayment)

应该

decPayment = Convert.ToDecimal(dblPayment)

来源

2014-12-08 14:04:31

由于Visual Basic中的按揭付款计算中收到“infinity”

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