Question

我的程序需要用户输入，如下所示：

Dim yesorno = InputBox("Do you have more credit cards?", "Thomas Shera")
    If yesorno = "Yes" Or "yes" Then
            Name = InputBox("You are a rich person, enjoy infinite credit card bill.")
    Else
        MsgBox("You poor person, you have only " & dcreditcards & " credit cards.")
    End If

违规第二行具体：

If yesorno = "Yes" Or "yes" Then

这给出了错误：

Microsoft.VisualBasic.dll中出现未处理的“System.InvalidCastException”类型异常

附加信息：从字符串“yes”到“Boolean”类型的转换无效。

想法修复这个如何，使“是”或“是”不会导致无效的错误异常？

Answer 1

是：

If yesorno = "Yes" Or yesorno = "yes" Then

但最好在StringComparison中使用正确的String.Equals：

If String.Equals(yesorno, "YES", StringComparison.CurrentCultureIgnoreCase) Then

您还应该使用OrElse而不是短路运营商：

If yesorno = "Yes" OrElse yesorno = "yes" Then

否则，即使第一个已经True，也会始终评估双方。这可能是一个问题，如：

If yesorno Is Nothing Or yesorno.Length = 0 Then

即使第一个表达式已经评估为true，它也会引发异常。

Answer 2

表达式（yesorno =“是”或“是”）求值为（Boolean或String）这会导致异常。正在将布尔值与字符串进行比较。

试试这段代码： -

Dim yesorno = InputBox("Do you have more credit cards?", "Thomas Shera")
If yesorno.ToUpper = "YES" Then
        Name = InputBox("You are a rich person, enjoy infinite credit card bill.")
Else
    MsgBox("You poor person, you have only " & dcreditcards & " credit cards.")
End If

“附加信息：从字符串”是“转换为”布尔“类型无效。”

2 个答案: