Regular Expression question

Question

When using the Regex.Replace() method how can I change the character case? For example, if I have some text that is all uppercase but I want to convert any XML entities such & to & string someText = "THIS & THAT."; // I want to change to THIS & THAT. What is the easiest way using an expression like: someText = Regex.Replace(someText, @"(?&\w+?;)", ${ent}); PERL scripts use a \L to lowercase the replacement text. I cannot seem to find something similar in the .NET regular expressions.