Regular Expressions

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nibsy

Regular
Joined
Aug 7, 2002
Messages
51
Location
Kent, UK
I am trying to validate an English postcode of the form XXXX XXX using regular expressions.

I think I may have something wrong with my pattern. I am new to regular expressions and would appreciate if somebody could point out any glaring errors.

Visual Basic: 
Dim pattern As String = "^\s*(\d{4}\s+\d{3})\s*$"
If Not Regex.IsMatch(txtPC.Text, pattern) Then
     ' Do Stuff
End If
[\VB]

Thanks in advance.
 
I don't know what the Input looks like (whether the postcode is between other words or not) but try it without the "^" and "$"... another point: the "Not" in you If-Clause... was that an accident? ;) or did I just not understand what you're trying to do? :D

Andreas
 
I'm not sure of the English format, but in the US the last 4 digits (not 3) are optional. If the last 3 are optional, you could change the expression.

Otherwise, it looks good. Personally, I'm not sure I'd want the "\s*" portions, as you'll have to manually trim off the whitespace to see the "real" data. I hate trimming, but it may be necessary for you. :)

-Nerseus
 
Thanks for the replies.

(Hamburger1984: The NOT in the IF clause only sets a boolean, as I intend to validate numerous input boxes :) )

Sorry, it appears I was testing the expression wrong!

Also, I needed to expand my expression somewhat to fully validate English post codes.

Here is the pattern I am using;

Visual Basic: 
Dim pattern As String = "[A-Z]{1,2}\d{1,2}\s?\d[A-Z]{2}"
 
Last edited:
I just want to make sure you know that that pattern will match the following string:

...RUNDLL32 1ST PROBLEM I FORESEE...

It will match the "LL32 1ST" part of it

If you would like to make it a bit more robust, you might want:

\b[A-Z]{1,2}\d{1,2}\s{1,3}\d[A-Z]{2}\b

I'm not familiar with the English post codes, but are all of the following valid? These would all be caught by the expression

A1 2BC
DE3 4FG
H56 7IJ
KL89 0MN
 
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