Question

我正在为一个课程项目开发预算计算器。基本上一切都很好，除了一点烦人的细微差别。

如果您未输入数字或输入负数，则会收到错误消息。但是，当你不小心输入一个字母时，得到错误，然后输入它刚刚退出的负数，我希望它显示该错误并循环回去，直到它们输入正数。

我在Visual Studio 2012中使用VBA，这是一个Windows窗体应用程序。

    Dim strEntertainmentHeading As String = "Entertainment Expenses"
    Dim strHeading As String = "Budget Alottment"
    Dim strNonNumericError As String = "Error - Enter a number for the Expense"
    Dim strNegativeError As String = "Error - Enter a positive number for the Expense"
    Dim strEntertainmentInput As String = "Enter the amount for Entertainment Expenses"
    Dim strEntertainment As String
    Dim decEntertainment As Decimal
    strEntertainment = InputBox(strEntertainmentInput, strEntertainmentHeading, " ")

    Do
        If strEntertainment = "" Then
            Exit Sub

        ElseIf IsNumeric(strEntertainment) Then
            decEntertainment = Convert.ToDecimal(strEntertainment)

            If decEntertainment >= 0 Then
                lstBudget.Items.Add("Entertainment Expense: " & decEntertainment.ToString("C2"))


                ' Display error message if user entered a negative value
            Else
                strEntertainmentInput = strNegativeError
            End If
        Else
            strEntertainmentInput = strNonNumericError
        End If

        If decEntertainment <= 0 Then
            strEntertainment = InputBox(strEntertainmentInput, strEntertainmentHeading, " ")
        End If

    Loop Until IsNumeric(strEntertainment) And decEntertainment >= 0

Answer 1

当然，你有这个问题：默认情况下decEntertainment为0，第二次请求输入后，你不再转换为.ToDecimal。

如果您采用明确的编码风格，例如

，则可以避免此类错误

Do 
    strEntertainmentInput = ''
    strEntertainment = InputBox(strEntertainmentInput, strEntertainmentHeading, " ")

    If Not IsNumeric(strEntertainment) Then
        strEntertainmentInput = strNonNumericError
    Else
        decEntertainment = Convert.ToDecimal(strEntertainment)
        If decEntertainment < 0 Then
            strEntertainmentInput = strNegativeError
        Else
            lstBudget.Items.Add("Entertainment Expense: " & decEntertainment.ToString("C2"))
        End
    End
Loop Until strEntertainmentInput = ''

Visual Basic保持在循环中验证InputBoxes

1 个答案: