Question

我遇到了应用程序的问题。当计算按钮点击事件应根据用户输入的5位数邮政编码显示相应的运费。为了有效，邮政编码必须包含5位数字，前3位数字必须为＆＃34; 605＆＃34;或＆＃34; 606＆＃34;。＆＃34; 605＆＃34;运费为25美元＆＃34; 606为30美元。如果邮政编码无效，则显示相应的消息。

我已经开始检查＆＃34; 605＆＃34;的邮政编码。或＆＃34; 606＆＃34;但如果我输入的数字少于5位，则给出零价而不是错误消息，所以我错过了一些东西。

感谢任何帮助或指导。感谢。

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 txtZip_Enter(sender As Object, e As EventArgs) Handles txtZip.Enter
    txtZip.SelectAll()
End Sub

Private Sub txtZip_TextChanged(sender As Object, e As EventArgs) Handles txtZip.TextChanged
    lblShipping.Text = String.Empty
End Sub

Private Sub btnDisplay_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click

    Dim strZip As String
    Dim dblShipping As Double

    strZip = txtZip.Text

    'Make sure zip code is 5 digits 
    If strZip.Length = 5 Then
        'Calculate the shipping based on first 3 digits
        If strZip Like "605##" Then
            dblShipping = 25.0
        ElseIf strZip Like "606##" Then
            dblShipping = 30.0
        Else
            MessageBox.Show("Invalid ZIP code, must be 5 digits and begin with 605 or 606")
        End If
    End If

    'display shipping charge
    lblShipping.Text = dblShipping.ToString("N2")

End Sub

结束班

Answer 1

您的Else未正确缩进，因此它似乎属于外部If strZip.Lenth = 5 Then语句而不是内部If strZip Like "505##" Then语句。我已编辑了您的问题以更正此缩进错误。

您可以看到，您还没有为用户提供其他输入时指定代码路径，并且在.NET中，数字值在声明时默认为0（即dblShipping默认情况下值为0.0，因此您看到的是零。

我建议这一点（注意早期失败的回报）

Dim lengthValid As Boolean = strZip.Length.Equals( 5 ) ' this is necessary as the = operator in VB.NET does not return a boolean value
Dim prefixValid As Boolean = strZip.StartsWith("605") OrElse strZip.StartsWith("607")
If Not lengthValid OrElse Not prefixValid Then
   MessageBox.Show("Invalid ZIP code, must be 5 digits and begin with 605 or 606")
   Return
Else
   If strZip.StartsWith("605") Then
       dblShipping = 25
   Else
       dblShipping = 30
   End If
End If

Visual Basic - 根据5位邮政编码验证显示送货

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