Why can't I match POSIX Character Classes

Question

The following snippet prints False:

Console.WriteLine(Regex.IsMatch("abc", @"[[:alpha:]]"));

But this prints True:

Console.WriteLine(Regex.IsMatch("abc", @"[a-zA-Z]"));

Why? Shouldn't they be equivalent?

Answer 1

.NET Regexes don't support the Posix character classes. They do however support Unicode groups.

This would work:

Regex.IsMatch("abc", @"^\p{L}+$");

The \p{L} group matches all Unicode letters.

See here for more information:

http://msdn.microsoft.com/en-us/library/20bw873z.aspx#CategoryOrBlock