vb.net 如何验证 Vb 中的文本框只允许 3 个数字和 2 个字母？
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How to validate a textbox in Vb to only allow 3 numbers and 2 letters?
提问by Philip Dyson
I figured out how too get only numbers in a text box with is code:
我想出了如何在带有代码的文本框中只获取数字：
Dim smessage As String = String.Empty
If Not IsNumeric(Student_IDTextBox.Text) Then
smessage += "The ID must be Numeric!" + Environment.NewLine
End If
But I would like this textbox to have 2 letters and 3 numbers, do you know what the best way to programme this in vb?
但我希望这个文本框有 2 个字母和 3 个数字，你知道在 vb 中编程的最佳方法是什么吗？
采纳答案by Pow-Ian
This is certainly not the bestway, but I do not know if you will ever find the bestway because bestis subjective and often dependent on more than one situation as well as opinion.
这当然不是最好的方法，但我不知道你是否会找到最好的方法，因为最好是主观的，而且往往取决于不止一种情况和意见。
Assuming a text box with the name txtinputand a label where you will be displaying the results named lblMessageand assuming you are using ASCII character input:
假设有一个带有名称txtinput和标签的文本框，您将在其中显示命名的结果lblMessage并假设您使用的是 ASCII 字符输入：
In the TextChangedevent of txtinputyou could have the following:
在TextChanged的情况下txtinput，你可以有以下几种：
'Check if the length is greater than five, if it is truncate it.
If txtinput.Text.Length > 5 Then
txtinput.Text = Mid(txtinput.Text, 1, 5)
txtinput.Select(txtinput.Text.Length, 0)
End If
'counters for letters and numbers
Dim letters As Integer = 0
Dim numbers As Integer = 0
'Parse and compare the input
For Each c As Char In txtinput.Text
If Asc(c) >= 48 And Asc(c) <= 57 Then 'ASCII characters for 0-9
numbers += 1
ElseIf Asc(c) >= 65 And Asc(c) <= 90 Then 'ASCII characters for A-Z
letters += 1
ElseIf Asc(c) >= 97 And Asc(c) <= 122 Then 'ASCII characters for a-z
letters += 1
End If
Next
If letters = 2 And numbers = 3 Then
lblMessage.Text = "Correct Format"
Else
lblMessage.Text = "Incorrect Format"
End If
Using Linq:
使用 Linq：
If txtinput.Text.Length > 5 Then
txtinput.Text = Mid(txtinput.Text, 1, 5)
txtinput.Select(txtinput.Text.Length, 0)
End If
If txtinput.Text.Count(Function(x As Char) Char.IsLetter(x)) = 3 And txtinput.Text.Count(Function(x As Char) Char.IsNumber(x)) = 2 Then
lblMessage.Text = "Correct Format"
Else
lblMessage.Text = "Incorrect Format"
End If
回答by jyothis
please try masked textbox with custom mask. set mask like- LLL00. refer this link http://msdn.microsoft.com/en-us/library/system.windows.forms.maskedtextbox.mask.aspx
请尝试使用自定义蒙版的蒙版文本框。像 LLL00 一样设置掩码。请参阅此链接 http://msdn.microsoft.com/en-us/library/system.windows.forms.maskedtextbox.mask.aspx
回答by ??ssa P?ngj?rdenlarp
If the ID must be 3 numerals and 2 characters than there is probablyalso a pattern to it (as with many license plates) and more important than the mere character type count. A masked text box is one way, counting the numerals and counting the letters is another.
如果 ID 必须是 3 个数字和 2 个字符，那么它可能还有一个模式（就像许多车牌一样）并且比单纯的字符类型计数更重要。屏蔽文本框是一种方法，计算数字和计算字母是另一种方法。
If there is a pattern such as AAA-NN or AAANN, you could split the ID into 2 inputs one alpha, one numeric. This is often done with IDs in patterns such as a (US) social security number (NNN-NN-NNNN). RegEx could also probably be used to test the pattern.
如果存在诸如 AAA-NN 或 AAANN 之类的模式，您可以将 ID 分成 2 个输入，一个是字母，一个是数字。这通常使用模式中的 ID 来完成，例如（美国）社会安全号码 (NNN-NN-NNNN)。RegEx 也可能用于测试模式。
If this is a login or otherwise a database app, rather than write too much code to simply test the patterntest the entry. You could collect whatever they type and do a simple query to see if the ID exists, which after all is far more important than the pattern.
如果这是登录或其他数据库应用程序，而不是编写太多代码来简单地测试模式测试条目。您可以收集他们输入的任何内容并执行简单的查询以查看 ID 是否存在，这毕竟比模式重要得多。
A label on the form can tell them to use ###AA or whatever, but it seems silly to test the pattern and report a pattern error when you can simply tell them when it is invalid. After all, even if it has the correct pattern, it can still be an invalid ID.
表单上的标签可以告诉他们使用###AA 或其他什么，但是当您可以简单地告诉他们无效时，测试模式并报告模式错误似乎很愚蠢。毕竟，即使它有正确的模式，它仍然可能是一个无效的 ID。
