Make regular expression case insensitive

Question

Given this regular expression: "^[0-9]*\s*(lbs|kg|kgs)$" how do I make it case insensitive? I am trying to use this in a .net regular expression validator, so I need to specify case insensitivity in the pattern.

I can not use the RegexOptions programatically because I am specifying the regular expression in a RegularExpressionValidator

Answer 1

Use RegEx Options.

Regex regExInsensitive = new Regex(@"^[0-9]\s(lbs|kg|kgs)$", RegexOptions.IgnoreCase);

In other languages you can usually specify a RegEx modifier after the end of the Reg Ex; the 'case insensitive' modifier is 'i':

In Perl:

if($var =~ /^[0-9]\s(lbs|kg|kgs)$/i) { # the /i means case insensitive
    # ...
}

In PHP:

if(preg_match("/^[0-9]\s(lbs|kg|kgs)$/i", $var)) {
    // ...
}

Answer 2

Easiest here is to just modify the regex to

^[0-9]*\s*([lL][bB][sS]|[kK][gG][sS]?)$

It's awful to read, but it will work fine.

Answer 3

I found out.

Case sensitive: ^[0-9]\s(lbs|kg|kgs)$

Case insensitive: (?i:^[0-9]\s(lbs|kg|kgs)$)

I believe that this is specific to the .net implementation of regular expressions. So if you use this in the RegularExpressionValidator you have to turn off client side validation because the javascript regex parser will not recognize the ?i token.