如何使用此可视化基本代码将列表框中的值四舍五入到小数点后两位

Question

I have written this code in visual basic to solve a basic interest calculation. The year end balances are shown in the list box and the final total is show in the label. My problem is that I can not figure out how to round the values in the list box to two decimals. I have tried various things but with no luck so far so I appreciate any help.

Public Class frmNestEgg Private Sub btnPrincipal_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click ' Declare and Initialize the variables

    Dim Principal As Double = txtPrincipal.Text
    Dim InterestRate As Double = txtInterestRate.Text / 100
    Dim Years As Integer
    Dim FinalTotal As Double
    Dim YrEndAmt As Double

    Years = Integer.Parse(txtYears.Text)

    'Calculate the interest from the principal payment over the years input to create a total value.
    For Years = 1 To Years
        FinalTotal = Principal * Math.Pow((1 + InterestRate), Years)
        YrEndAmt = (FinalTotal - Principal) + Principal
        lstYrEndAmt.Items.Add("Year" & Years & " Balance " & YrEndAmt)
        lblFinalTotal.Visible = True
        lblFinalTotal.Text = FinalTotal.ToString("f1")
    Next


End Sub

Private Sub frmNestEgg_Load(sender As Object, e As EventArgs) Handles MyBase.Load

End Sub

End Class

Answer 1

you could use

Math.Round() 
... & Math.Round(YrEndAmt, 2).ToString()

but your code had a flaw: same variable Years for looping and end condition

so change:

    For Years = 1 To Years

to:

    Dim Years As Integer, year As Integer

    For year = 1 To Years

your entire code would then be:

Private Sub btnPrincipal_Click(sender As Object, e As EventArgs) Handles btnPrincipal.Click
    Dim Principal As Double = txtPrincipal.Text
    Dim InterestRate As Double = txtInterestRate.Text / 100
    Dim Years As Integer, year As Integer
    Dim FinalTotal As Double
    Dim YrEndAmt As Double

    Years = Integer.Parse(txtYears.Text)

    'Calculate the interest from the principal payment over the years input to create a total value.
    For year = 1 To Years
        FinalTotal = Principal * Math.Pow((1 + InterestRate), Years)
        YrEndAmt = (FinalTotal - Principal) + Principal
        lstYrEndAmt.Items.Add("Year" & year & " Balance " & Math.Round(YrEndAmt, 2).ToString())
        lblFinalTotal.Visible = True
        lblFinalTotal.Text = FinalTotal.ToString("f1")
    Next
End Sub