为什么Windows 10使此代码产生InvalidCastException [英] Why is Windows 10 making this code give an InvalidCastException

问题描述

以下代码片段在Windows 7专业版上运行时效果非常好但在Windows 10上运行时会抛出无效的强制转换异常。

任何想法微软改变了什么以及我需要做些什么才能获得它在Win10上工作吗？

这是我的一个朋友在Win10 pc和它上面运行它我没有在我的电脑上:-)



非常感谢，

Tim



**************异常文本**************

The following code snippet works absolutely great when run on Windows 7 professional BUT throws an Invalid Cast Exception when run on Windows 10.
Any idea what Microsoft have changed and what I need to do to get it working on Win10?
It's a friend of mine running it on a Win10 pc & I don't have it on my pc :-)

Many thanks,
Tim

************** Exception Text **************

System.InvalidCastException: Conversion from string "£0.00" to type 'Decimal' is not valid.
   at Microsoft.VisualBasic.CompilerServices.Conversions.ToDecimal(String Value, NumberFormatInfo NumberFormat)
   at Microsoft.VisualBasic.CompilerServices.Conversions.ToDecimal(String Value)
   at GtracsX4.gtac1b.tBox_Validating(Object sender, CancelEventArgs e)

代码

The Code

Private Sub tBox_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles _
      amtInp.Validating, DescInp.Validating, RefInp.Validating
    Dim mtb As String = sender.tag : Dim mtbx As TextBox = sender : Dim ta As Decimal
    If mtb = "dec" Then
        If (String.IsNullOrEmpty(mtbx.Text)) Then mtbx.Text = "0"
        If IsNumeric(mtbx.Text) = False Then
            msgM = "Only NUMBERS allowed.  Please re-enter"
            msg = New gtzMess(1, "", msgM, "OK", "", "", "S")   '   flags = ISQW
            msg.ShowDialog()
            mtbx.Text = 0
            e.Cancel = True
            Exit Sub
        End If
        ta = CDec(mtbx.Text)
        mtbx.Text = "£" & ta.ToString("N2")
        If mtbx.Name = "amtInp" Then tAmt.Text = CDec(mtbx.Text)
    End If
End Sub

推荐答案

你为什么这样做？

看看你的代码：

Why are you doing that?
Look at your code:

ta = CDec(mtbx.Text)
mtbx.Text = "£" & ta.ToString("N2")
If mtbx.Name = "amtInp" Then tAmt.Text = CDec(mtbx.Text)

ta = CDec(mtbx.Text)

取一个文本框值，然后转换它到十进制。这个想法很糟糕：你应该使用Decimal.TryParse并向用户报告问题。

Take a Textbox value, and convert it to a Decimal. This is a poor idea: you should be using Decimal.TryParse and reporting problems to the user.

mtbx.Text = "£" & ta.ToString("N2")

将它转换为十进制值后，立即将其转换回tring，并在前面加上货币符号。

Having converted it to a decimal value, you immediately convert it back to a tring, and tack a currency symbol on the front.

If mtbx.Name = "amtInp" Then tAmt.Text = CDec(mtbx.Text)

然后你将它转换回一个十进制（如果它不会导致它失败，它将丢弃该货币），以便将其转换回一个字符串，将其放入文本框。



那是......嗯......很奇怪。

使用TryParse转换它（带报告），看看你想要存储在哪里 - 你最多需要两种类型的转换：一个到一个dec，一个到一个字符串。这只是因为你指定了字符串值的格式！

你的问题会在同一时间消失。

You then convert that back to a decimal (which will throw away the currency, if it doesn't cause it to fail, which it does) in order to convert it back into a string, to put it in a textbox.

That's...um...very odd.
Use TryParse to convert it (with reporting), and look at what you are trying to store where - you should need at most two type conversions: one to a dec, and one to a string. And that's only because your specify a format for the string value!
And your problem will go away at the same time.

它与Windows版本无关，它与您描述的两种不同情况下设置的不同默认文化有关。您的代码应该是文化中立的，或者您必须在应用程序本身强制某些固定的文化，这是一个每个线程的选项：

https://msdn.microsoft.com/en-us/library/system.threading.thread.currentculture （v = vs.110）.aspx [ ^ ]，

https://msdn.microsoft.com/en-us/library/system.threading.thread.currentuiculture（v = vs.110）的.aspx [ ^ ]。

-SA

It is not related to Windows version, it's related to the different default culture set up in two different cases you described. Your code should either be culture-neutral, or you have to force certain fixed culture in the application itself, which is a per-thread option:
https://msdn.microsoft.com/en-us/library/system.threading.thread.currentculture(v=vs.110).aspx[^],
https://msdn.microsoft.com/en-us/library/system.threading.thread.currentuiculture(v=vs.110).aspx[^].

—SA

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