从字符串 "" 到类型 'Integer' 的转换无效。- VB.NET
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Conversion from string "" to type 'Integer' is not valid. - VB.NET
提问by nirosha rathnayaka
When I click cancel button of the input box it shows this 'Conversion from string "" to type 'Integer' is not valid.' error in vb.net 2010. My code is,
当我单击输入框的取消按钮时，它显示此“从字符串“”转换为类型“整数”无效。vb.net 2010 中的错误。我的代码是，
Dim lineNo As Integer
lineNo = InputBox("What is the last record number?" &
vbNewLine & vbNewLine & "Enter line number 0 - 30.", "Enter Line Number", 0)
What's the wrong in here?
这里有什么问题？
Update: Dim lineNo As Integer. I have forgotten to state the declaration here.
更新：Dim lineNo As Integer。我忘记在这里声明声明了。
回答by Carlos Landeras
Declare lineNoas string:
声明lineNo为字符串：
Dim lineNo As String = InputBox("What is the last record number?" &
vbNewLine & vbNewLine & "Enter line number 0 - 30.", "Enter Line Number", 0)
lineNomust be declared as integer somewhere else in your code. Just pasted my code
on visual studio and no complaints.
lineNo必须在代码中的其他地方声明为整数。刚刚在visual studio上粘贴了我的代码，没有任何抱怨。
Even use another string variable if you need lineNo as integer.
如果需要 lineNo 作为整数，甚至可以使用另一个字符串变量。
回答by Alexander
I presume lineNo is declared as Integer? Clicking "Cancel" on the InputBox will return an empty string, and an emptry string cannot be converted to a numeric value. That's what your error says.
So you should get the result of the InputBox, which always returns a String, and convert it in a separate step, maybe with Integer.TryParse.
我认为 lineNo 被声明为整数？在 InputBox 上点击“取消”将返回一个空字符串，空字符串不能转换为数值。这就是你的错误所说的。所以你应该得到 InputBox 的结果，它总是返回一个字符串，并在一个单独的步骤中转换它，也许用Integer.TryParse.
回答by matzone
since your inputbox return string so you have to do
因为你的输入框返回字符串所以你必须做
lineNo = val(InputBox("What is the last record number?" & vbNewLine & vbNewLine & "Enter line number 0 - 30.", "Enter Line Number", 0))
