System.Text.RegularExpressions.RegexCharClass.IsECMAWordChar C# (CSharp) Method

        internal static bool IsECMAWordChar(char ch) {
            return CharInClass(ch, ECMAWordClass);
        }

 protected bool IsECMABoundary(int index, int startpos, int endpos)
 {
     return((index > startpos && RegexCharClass.IsECMAWordChar(_runtext[index - 1])) !=
            (index < endpos && RegexCharClass.IsECMAWordChar(_runtext[index])));
 }