This is sort of a computer science question and sort of a programming question. What is the name of the formal class of languages that can be described by .NET regular expressions (assuming it a well known class)? For instance formal regular expressions describe the class of regular languages but .NET regular expressions (as with most modern regular expression engines) are more powerful than formal regular expressions and therefore describe a larger class of languages.
This is basically the same question as this Which languages do Perl-compatible regular expressions recognize? but for .NET regular expressions instead of perl regular expressions. However as far as I can tell, this question was never answered completely either.