使用financial.ppmt方法的贷款计算器

Question

任务是让用户输入本金金额，并从组合框中选择利率以及条款。UI应该在标签中显示每月付款，以及在多行文本框中支付给本金和利息的金额。我在完成代码时遇到了麻烦。我不太确定我是否没有完全得到financial.ppmt方法，或者不仅仅是我的月付款显示不准确，但我无法正确地显示多行文本框信息(本金和利息金额)。如果有人能帮我，或者至少指点我一个类似的项目，我会非常感谢的！

Option Explicit On
Option Strict On
Option Infer Off


Public Class MainForm
Private Sub ExitButton_Click(sender As Object, e As EventArgs) Handles ExitButton.Click
    Me.Close()

End Sub

Private Sub CalcButton_Click(sender As Object, e As EventArgs) Handles CalcButton.Click
    'Calculates the monthly payments on a loan using 
    'annual interest rates from 2%-10% and terms from 1-30 years

    Dim Principal As Double
    Dim term As Integer
    Dim rate As Double
    Dim monthlyPayment As Double
    Dim interest As Double

    'assign input to variables
    Double.TryParse(PrincipalTextBox.Text, Principal)
    term = Convert.ToInt32(TermComboBox.SelectedItem)

    'clear text boxes
    PaymentValue.Text = String.Empty
    PrincipleAndInterestBox.Text = String.Empty

    'calculate and display monthly payments
    monthlyPayment = -Financial.Pmt(rate / 12, 12, term * 12, Principal)
    MonthlyPaymentLabel.Text = monthlyPayment.ToString("C2")

    'Calculate the amount applied to principal and interest
    For per As Integer = 12 To 1 Step -1
        Principal = -Financial.PPmt(rate / 12, per, 12, Principal)
        interest = monthlyPayment - Principal
        PrincipleAndInterestBox.Text = Principal.ToString("C2") & "         " & interest.ToString("C2") & ControlChars.NewLine

    Next per
    PrincipleAndInterestBox.Focus()
End Sub

Private Sub MainForm_Load(sender As Object, e As EventArgs) Handles Me.Load
    'fill termComboBox
    For term As Integer = 1 To 30
        TermComboBox.Items.Add(term.ToString)
    Next term
    TermComboBox.SelectedItem = "10"

    'fill interestRateComboBox
    For rate As Integer = 2 To 10
        InterestRateComboBox.Items.Add(rate.ToString)
    Next rate
    InterestRateComboBox.SelectedItem = "4"
End Sub

端级

Answer 1

转到textbox属性并选择multiline = true

在循环中，您正在为textbox分配新值，而忽略了现有值。

PrincipleAndInterestBox.Text = PrincipleAndInterestBox.Text & Principal.ToString("C2") & "         " & interest.ToString("C2") & ControlChars.NewLine

或

textBox1.Multiline = True
textBox1.ScrollBars = ScrollBars.Vertical
textBox1.WordWrap = True
textBox1.Text = "Welcome!" & Environment.NewLine & "Second Line"