How to make a regex match case insensitive?

Solution 1:

Just use the option IgnoreCase, see .NET regular Expression Options

So your regex creation could look like this

Regex r = new Regex(@"^[ABCEGHJKLMNPRSTVXY]\d[A-Z] *\d[A-Z]\d$", RegexOptions.IgnoreCase);

I removed also all your {1} because it is superfluous. Every item is per default matched once, no need to state this explicitly.

The other possibility would be to use inline modifiers, when you are not able to set it on the object.

^(?i)[ABCEGHJKLMNPRSTVXY]\d[A-Z] *\d[A-Z]\d$