我正在编写一个简单的程序,教科书要我在程序中使用string.TrimStart()和string.TrimEnd()方法。您将金额输入到txtSales,然后在lstRates中选择适当的销售税,按计算按钮,它会计算您需要支付多少税,并将其显示在lblTax中。现在,似乎无论我用什么方法做到这一点,lstRates总是返回0 ..有什么建议吗?
Option Explicit On
Option Strict On
Option Infer Off
Public Class frmMain
Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
Me.Close()
End Sub
Private Sub txtSales_Enter(sender As Object, e As EventArgs) Handles txtSales.Enter
txtSales.SelectAll()
End Sub
Private Sub lstRates_SelectedValueChanged(sender As Object, e As EventArgs) Handles lstRates.SelectedValueChanged
lblTax.Text = String.Empty
End Sub
Private Sub txtSales_TextChanged(sender As Object, e As EventArgs) Handles txtSales.TextChanged
lblTax.Text = String.Empty
End Sub
Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles Me.Load
' fills the list box with tax rates
For dblRate As Double = 0.02 To 0.1 Step 0.01
lstRates.Items.Add(dblRate.ToString("P0"))
Next dblRate
lstRates.SelectedIndex = 0
End Sub
Private Sub btnCalc_Click(sender As Object, e As EventArgs) Handles btnCalc.Click
Dim dblSales As Double
Dim dblRates As Double
Dim strRates As String
Double.TryParse(txtSales.Text, dblSales)
strRates = lstRates.Text
strRates = strRates.TrimEnd("%"c)
Double.TryParse(strRates, dblRates)
Double.TryParse(lstRates.Text, dblRates)
lblTax.Text = (dblSales * dblRates).ToString
End Sub
结束班
答案 0 :(得分:0)
删除了Double.TryParse(lstRates.Text,dblRates)并添加了dblRates * = 0.01 奇迹般有效!
Private Sub btnCalc_Click(sender As Object, e As EventArgs) Handles btnCalc.Click
Dim dblSales As Double
Dim dblRates As Double
Dim strRates As String
Double.TryParse(txtSales.Text, dblSales)
strRates = lstRates.Text
strRates = strRates.TrimEnd("%"c)
Double.TryParse(strRates, dblRates)
dblRates *= 0.01
lblTax.Text = (dblSales * dblRates).ToString("C2")
End Sub