为什么这段代码会抛出 FormatException？

发布于 2024-10-15 05:45:13 字数 551 浏览 9 评论 0原文

我编写了以下代码：

 Dim E_ID As Integer
 E_ID = Convert.ToInt16(Request.QueryString("ID"))

但是当它执行时，我总是得到一个FormatException：

错误：输入字符串的格式不正确。

可能是什么原因造成的？

我正在发送这样的值。

Protected Sub lnkPrint_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles lnkPrint.Click
        lnkPrint.Attributes.Add("onclick", "return openBadgeReportPage('" + ddEvent.DataValueField + "','" + ddType.DataValueField + "')")
    End Sub
End Class

原文

I have written the following code:

 Dim E_ID As Integer
 E_ID = Convert.ToInt16(Request.QueryString("ID"))

But when it executes, I always get a FormatException:

error: Input string was not in a correct format.

What could be causing this?

i am sending value like this.

Protected Sub lnkPrint_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles lnkPrint.Click
        lnkPrint.Attributes.Add("onclick", "return openBadgeReportPage('" + ddEvent.DataValueField + "','" + ddType.DataValueField + "')")
    End Sub
End Class

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泪之魂 2024-10-22 05:45:13

因为 Request.QueryString("ID") 函数调用返回的任何值都不能转换为 Int16 类型。根据 Convert.ToInt16 方法的文档，FormatException 是每当出现以下情况时抛出：

值不包含可选符号后跟数字序列（0 到 9）。

您可以通过将代码分成几行并设置断点来查看实际返回的值。例如：

Dim E_ID As Integer
Dim queryString As String
queryString = Request.QueryString("ID")    ' <-- place breakpoint here
E_ID = Convert.ToInt16(queryString)

Because whatever value is being returned by the Request.QueryString("ID") function call is not convertible to an Int16 type. According to the documentation for the Convert.ToInt16 method, a FormatException is thrown whenever the:

value does not consist of an optional sign followed by a sequence of digits (0 through 9).

You can see what value is actually being returned by separating your code out into a couple of different lines, and setting a breakpoint. For example:

Dim E_ID As Integer
Dim queryString As String
queryString = Request.QueryString("ID")    ' <-- place breakpoint here
E_ID = Convert.ToInt16(queryString)

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自找没趣 2024-10-22 05:45:13

这里需要注意两件事：

1）您尝试将 Int16 分配给 Integer（默认情况下为 32 位）。这是一个有效的操作，但是您有可能在应用程序中引入错误。

2）正如 Cody 提到的，Request.QueryString("ID") 返回的值可能无法转换为 Int16，因此会出现错误。您可以尝试以下代码以更安全的方式验证 Request.QueryString("ID") 语句返回的值：

Dim E_ID As Int16
Boolean isInteger = Int16.TryParse(Request.QueryString("ID"), out E_ID)

If isInteger Then
     // you have a valid short int inside the E_ID variable now.

There are 2 things you need to note here:

1) You are trying to assign an Int16 to an Integer (32 bit by default). This is a valid operation, however there is a chance you could introduce a bug in your application.

2) As Cody mentioned the value returned by Request.QueryString("ID") may not be convertible to an Int16 and hence the error. You can try the following code to verify the value returned by the Request.QueryString("ID") statement in a safer way:

Dim E_ID As Int16
Boolean isInteger = Int16.TryParse(Request.QueryString("ID"), out E_ID)

If isInteger Then
     // you have a valid short int inside the E_ID variable now.

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