Case insensitive Regex without using RegexOptions enumeration

Question

Is it possible to do a case insensitive match in C# using the Regex class without setting the RegexOptions.IgnoreCase flag?

What I would like to be able to do is within the regex itself define whether or not I want the match operation to be done in a case insensitive manner.

I would like this regex, taylor, to match on the following values:

• Taylor
• taylor
• taYloR

Answer 1

MSDN Documentation

(?i)taylor matches all of the inputs I specified without having to set the RegexOptions.IgnoreCase flag.

To force case sensitivity I can do (?-i)taylor.

It looks like other options include:

• i, case insensitive
• s, single line mode
• m, multi line mode
• x, free spacing mode

Answer 2

As you already found out, (?i) is the in-line equivalent of RegexOptions.IgnoreCase.

Just FYI, there are a few tricks you can do with it:

Regex:     a(?i)bc Matches:     a       # match the character 'a'     (?i)    # enable case insensitive matching     b       # match the character 'b' or 'B'     c       # match the character 'c' or 'C'  Regex:     a(?i)b(?-i)c Matches:     a        # match the character 'a'     (?i)     # enable case insensitive matching     b        # match the character 'b' or 'B'     (?-i)    # disable case insensitive matching     c        # match the character 'c'  Regex:         a(?i:b)c Matches:     a       # match the character 'a'     (?i:    # start non-capture group 1 and enable case insensitive matching       b     #   match the character 'b' or 'B'     )       # end non-capture group 1     c       # match the character 'c' 

And you can even combine flags like this: a(?mi-s)bc meaning:

a          # match the character 'a' (?mi-s)    # enable multi-line option, case insensitive matching and disable dot-all option b          # match the character 'b' or 'B' c          # match the character 'c' or 'C'