Regular Expression and RegEx Obj.

BrianWren · August 1st, 2008, 01:52 PM

I am trying to verify that a textbox contains nothing but A-Z, a-z and 0-9.

I tried

Code:

    Dim RegExObj As New _
        System.Text.RegularExpressions.Regex("^A-Za-z0-9") 

    MsgBox("Match: " & RegExObj.IsMatch(TxtBx.Text))

But this didn't really work for me.

With "abc" I got False. (Perfect.) With abc% I got False. (No good.)

There is no shortage of examples for how to do everything except what it is that I want to do (as usual)...

Old Pedant · August 1st, 2008, 02:53 PM

Try this:

Dim RegExObj As New _
        System.Text.RegularExpressions.Regex("[^A-Za-z0-9]")

The ^ character at the beginning of the expression means "start of text". There is no "grouping" of the characters implied. So your expression was really looking for the *LITERAL STRING*
     A-Za-z0-9
to start the text. In other words
     "A-Za-z0-9 zambonis rule"
would pass. But you would need those first 9 characters *exactly* as is to pass.

It's only when you use the character grouper [...] that the ^ takes on the meaning of "NOT" (or, as I like to think of it, [^xyz] means "any EXCEPT xyz").

BrianWren · August 1st, 2008, 04:03 PM

Thanks; that did the trick.

These Regular Expressions are mindbenders.