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我正在制作一个程序，允许用户查看歌曲信息、播放其中的片段并购买选定的歌曲。

并允许用户点击购买按钮购买指定的曲子。

退房时：

如果用户没有购买任何曲子，他们将无法结帐，但他们可以退出程序。

使用 InputBox 以便用户可以输入他们的销售税率。由于用户正在输入一个值，因此您必须对他们的输入执行数据验证。

允许用户通过单击 InputBox Cancel 按钮取消签出过程。

当输入框显示时，文本框应该有焦点，当添加了错误的税值时，错误的值应该被清除，文本框应该重新获得焦点。

使用 Write/Writeline 创建一个名为 PurchaseOrder.txt 的采购订单文本文件，其中包括文件的创建日期和采购清单、小计、税收和总计。

和以前一样的问题，但输入框没有出现。在我的代码中查找cmdCheckOut_Click子例程并找到以下内容：

str1 = InputBox("Enter your tax rate as a % between and including 0 - 10:", "Tax Rate", "", -1, -1)

我的代码：

Public Structure musicInfo
  <VBFixedString(30)> Public title As String
  <VBFixedString(20)> Public artist As String
  <VBFixedString(20)> Public genre As String
  <VBFixedString(10)> Public duration As String
  Public year As Integer
  Public price As Double
  <VBFixedString(15)> Public songFileName As String
End Structure

Public Const NoOfTunes = 5
Public songs(NoOfTunes - 1) As musicInfo

Option Explicit On
Imports System.IO
  Public Class frmTunes
  Public index As Integer
  Public purchaseCount As Integer
  Public purchasePrice(10) As Decimal
  Public purchaseTitle(10) As String
  Dim decimal1 As Decimal
  Dim decimal3 As Decimal
  Dim decimal4 As Decimal

Private Sub frmTunes_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    Dim i As Integer

    FileOpen(1, "music.dat", OpenMode.Random, , , Len(songs(0)))
    For i = 0 To NoOfTunes - 1
        FileGet(1, songs(i))
    Next
    FileClose(1)

    cmdPrevious.Visible = False

    DisplaySong(0)
End Sub

Sub DisplaySong(ByVal i As Int32)
    lblTitle.Text = songs(i).title
    lblArtist.Text = songs(i).artist
    lblGenre.Text = songs(i).genre
    lblDuration.Text = songs(i).duration
    lblYear.Text = Convert.ToString(songs(i).year)
    lblPrice.Text = Convert.ToString(songs(i).price)
End Sub

Private Sub cmdStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdStop.Click
    My.Computer.Audio.Stop()
End Sub

Private Sub cmdPurchase_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPurchase.Click
    purchaseTitle(purchaseCount) = lblTitle.Text
    purchasePrice(purchaseCount) = Convert.ToDecimal(lblPrice.Text)
    purchaseCount = (purchaseCount + 1)
End Sub

Private Sub cmdPrevious_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPrevious.Click
    index = (index - 1)
    If (index < 4) Then
        cmdNext.Visible = True
    End If
    If (index = 0) Then
        cmdPrevious.Visible = False
    End If
    DisplaySong(index)
End Sub

Private Sub cmdNext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdNext.Click
    index = (index + 1)
    If (index = NoOfTunes - 1) Then
        cmdNext.Visible = False
    End If
    If (index > 0) Then
        cmdPrevious.Visible = True
    End If
    DisplaySong(index)
End Sub

Private Sub cmdPlay_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPlay.Click
    My.Computer.Audio.Play(songs(index).songFileName)
End Sub

Private Sub cmdCheckOut_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdCheckOut.Click
    Dim str1 As String = ""
    If (purchaseCount = 0) Then
        MsgBox("You have not ordered any items!", MsgBoxStyle.Exclamation, "Order Error")
    Else
        Do While ((IsNumeric(str1) Or (Decimal.Compare(decimal3, Decimal.Zero) < 0)) Or (Decimal.Compare(decimal3, (10D)) > 0))
            str1 = InputBox("Enter your tax rate as a % between and including 0 - 10:", "Tax Rate", "", -1, -1)
            If (str1 <> "") Then

            End If
            If (IsNumeric(str1)) Then
                MsgBox("You must enter a numeric tax rate", MsgBoxStyle.Exclamation, "Tax Rate Error")
            Else
                Dim decimal3 As Decimal = Convert.ToDecimal(str1)
                If ((Decimal.Compare(decimal3, Decimal.Zero) < 0) Or (Decimal.Compare(decimal3, (10D)) > 0)) Then
                    MsgBox("You must enter a tax rate between and including 0% - 10%", MsgBoxStyle.Exclamation, "Tax Rate Error")
                End If
            End If
        Loop
        Dim StreamWriter As StreamWriter = File.CreateText("PurchaseOrder.txt")
        StreamWriter.WriteLine("For Purchases dated: " & DateTime.Now.ToLongDateString())
        StreamWriter.WriteLine()
        Dim num2 As Integer = (purchaseCount - 1)
        Dim num1 As Integer = 0
        Do While (num1 <= num2)
            StreamWriter.Write(Strings.FormatCurrency(CType(Me.purchasePrice(num1), Decimal) & vbTab & "     "))
            StreamWriter.WriteLine(purchaseTitle(num1))
            Dim decimal1 As Decimal = Decimal.Add(Nothing, purchasePrice(num1))
            num1 = (num1 + 1)

        Loop
        StreamWriter.WriteLine("------")
        StreamWriter.WriteLine(Strings.FormatCurrency(CType(decimal1, Decimal)) & " Subtotal")
        Dim decimal2 As Decimal = New Decimal(((Convert.ToDouble(decimal3) * 0.01) * Convert.ToDouble(decimal1)))
        StreamWriter.WriteLine(Strings.FormatCurrency(CType(decimal2, Decimal)) & "  Tax")
        StreamWriter.WriteLine("------")
        Dim decimal4 As Decimal = Decimal.Add(decimal1, decimal2)
        StreamWriter.WriteLine(Strings.FormatCurrency(CType(decimal4, Decimal)) & "  Total")
        MsgBox("Purchase Order has been created", MsgBoxStyle.OkOnly)
        StreamWriter.Close()
        Me.Close()
    End If
End Sub
End Class
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1 回答 1

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所以，你的问题出在这一行：

Do While ((IsNumeric(str1) Or (Decimal.Compare(decimal3, Decimal.Zero) < 0)) Or (Decimal.Compare(decimal3, (10D)) > 0))

您的条件未得到满足，因此循环内的代码永远不会运行。

于 2013-11-06T21:30:18.657 回答