public static extern int Search(this string str, RegExp regex);
public static extern string[] Split(this string str, RegExp separator, int limit);
public static extern string Replace(this string str, RegExp regexp, Func <string, int, string, string> function);
public static extern string[] Match(this string str, RegExp regex);
public static extern string Replace(this string str, RegExp regexp, Delegate function);
public static extern string Replace(this string str, RegExp regexp, string newSubStr);