Creating an Alphanumeric plus underscore Masked Text Box for DB Table Names

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Hi,

I want to create an input box for database table names. As such I don't want to allow spaces or special characters but I do want to allow the Underscore, numbers or letters.

I tried putting the following into the keypress event

VB

Dim allowedChars As String = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_"

If allowedChars.IndexOf(e.KeyChar) = -1 Then
    ' Invalid Character
    e.Handled = True
End If

which was really close but I found that the backspace key wouldn't work which made me nervous about user acceptance ...

So am I on the right track but need more tweaking to get this working or is there another solution that I'm not aware of? (I'm still pretty new to .Net)

Thanks.

Posted 21-Sep-11 10:15am

BHort

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Mario Majčica · Accepted Answer · 2011-09-21T10:59:00

Solution 1

Did you tried something like this?

VB

Collapse | Copy Code
Dim allowedChars As String = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_"

If allowedChars.IndexOf(e.KeyChar) = -1 Or e.KeyChar = Convert.ToChar(Keys.Back) Then
    ' Invalid Character
    e.Handled = True
End If

Cheers!

Posted 21-Sep-11 10:59am

Mario Majčica

Comments

BHort 21-Sep-11 17:04pm

Just did ... no joy. I thought it was because it would skip the back with the logic you supplied but putting NOT around the 2nd half didn't help ... but I think you might be on the right track ... I'll keep trying ...

BHort 21-Sep-11 17:10pm

Got it.

The correct If should be:
If allowedChars.IndexOf(e.KeyChar) = -1 And e.KeyChar <> Convert.ToChar(Keys.Back) Then

So the complete solution is to paste:

Dim allowedChars As String = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_"

If allowedChars.IndexOf(e.KeyChar) = -1 AND e.KeyChar <> Convert.ToChar(Keys.Back) Then
' Invalid Character
e.Handled = True
End If

Into the KeyPress event of a text box.

Hope this helps someone else. I really like it because it means my input testing is done up front.

Mario Majčica 22-Sep-11 1:06am

Great, sorry but grappa last evening fooled up my logic!