如果语句未给出正确答案ASP.NET

debugcn 发表于 Dev

AH5811

我目前正在尝试在if / else语句中查找错误，我进行了一些小测试，以查看变量是否包含值，但这些值都保持不变，但是当我单击“提交”按钮时，该值一直为零。

Partial Class _Default
    Inherits System.Web.UI.Page

Protected Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles Pack_Weight.TextChanged

End Sub

Protected Sub Submit_Button_Click(sender As Object, e As EventArgs) Handles Submit_Button.Click
    Dim PackageW, MemphisRate, SanFranRate As Double

    'takes user input from the textbox and places it in the variable
    PackageW = Pack_Weight.Text

    'if user selects the dropbox and radiobutton list the selected combo should charge a varying bag fee
    If Location.SelectedValue = "1" & ShippingList.SelectedValue = "1" Then
        MemphisRate = 2.2 * PackageW

    ElseIf Location.SelectedValue = "1" & ShippingList.SelectedValue = "2" Then
        MemphisRate = 2.59 * PackageW

    ElseIf Location.SelectedValue = "1" & ShippingList.SelectedValue = "3" Then
        MemphisRate = 2.92 * PackageW

    End If
    'outputs the user selected combo to the total amount textbox
    Total_Cost.Text = MemphisRate

    If Location.SelectedValue = "2" & ShippingList.SelectedValue = "1" Then
        SanFranRate = 2.2 * PackageW

    ElseIf Location.SelectedValue = "2" & ShippingList.SelectedValue = "2" Then
        SanFranRate = 2.59 * PackageW

    ElseIf Location.SelectedValue = "2" & ShippingList.SelectedValue = "3" Then
        SanFranRate = 2.92 * PackageW

    End If

    Total_Cost.Text = SanFranRate

End Sub
End Class

安德鲁·莫顿

您应在尝试处理输入之前执行输入验证。

使用Option Strict On将确保所有数据类型匹配，例如，它将阻止您尝试将字符串分配给数字变量。

在计算货币值时，最好使用Decimal类型而不是Double。

里面有很多If... ElseIfs-使用起来看起来会更整洁Select Case，像这样：

Option Strict On
' ...

Protected Sub Submit_Button_Click(sender As Object, e As EventArgs) Handles Submit_Button.Click
    Dim packageW As Decimal

    ' INPUT VALIDATION
    If Not Decimal.TryParse(Pack_Weight.Text, packageW) Then
        ' inform user that a number is required
        Exit Sub
    End If

    If Location.SelectedIndex = -1 Then
        ' inform user that a location must be selected
        Exit Sub
    End If

    If ShippingList.SelectedIndex = -1 Then
        ' inform user that a shipping type must be selected
        Exit Sub
    End If

    ' CALCULATE SHIPPING COST
    Dim shippingRate As Decimal = 0D

    Select Case Location.SelectedItem.Text
        Case "1" ' Memphis
            Select Case ShippingList.SelectedItem.Text
                Case "1" ' Economy
                    shippingRate = 2.2D
                Case "2" ' Normal
                    shippingRate = 2.59D
                Case "3" ' Speedy
                    shippingRate = 2.92D
            End Select

        Case "2" ' San Francisco
            Select Case ShippingList.SelectedItem.Text
                Case "1"
                    shippingRate = 2.2D
                Case "2"
                    shippingRate = 2.59D
                Case "3"
                    shippingRate = 2.92D
            End Select

    End Select

    Dim shippingCost As Decimal = Math.Round(packageW * shippingRate, 2)
    Total_Cost.Text = shippingRate.ToString()

End Sub

我发现.SelectedItem.Text比更加可靠.SelectedValue。

对我来说，尚不清楚某些变量的好名字-您应该对其进行更改以使其有意义。

从代码中的注释中还不清楚，没有选择的状态是否有效-如果是这样，请检查.SelectedIndex = 1。您可能要确保用户输入了有效值packageW，即不是负数，并且输入的大小也不合理。

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