Boo.Lang.Compiler.TypeSystem.NameResolutionService.ToSoundex C# (CSharp) Method

        private static string ToSoundex(string s)
        {
            if (s.Length < 2) return null;
            char[] code = "?0000".ToCharArray();
            string ws = s.ToLowerInvariant();
            int wsLen = ws.Length;
            char lastChar = ' ';
            int lastCharPos = 1;

            code[0] = ws[0];
            for (int i = 1; i < wsLen; i++)
            {
                char wsc = ws[i];
                char c = ' ';
                if (wsc == 'b' || wsc == 'f' || wsc == 'p' || wsc == 'v') c = '1';
                if (wsc == 'c' || wsc == 'g' || wsc == 'j' || wsc == 'k' || wsc == 'q' || wsc == 's' || wsc == 'x' || wsc == 'z') c = '2';
                if (wsc == 'd' || wsc == 't') c = '3';
                if (wsc == 'l') c = '4';
                if (wsc == 'm' || wsc == 'n') c = '5';
                if (wsc == 'r') c = '6';
                if (c == lastChar) continue;
                lastChar = c;
                if (c == ' ') continue;
                code[lastCharPos] = c;
                lastCharPos++;
                if (lastCharPos > 4) break;
            }
            return new string(code);
        }