public static String getSchemePrefix(String spec) {int colon = spec.indexOf(':');if (colon < 1) {return null;}for (int i = 0; i < colon; i++) {char c = spec.charAt(i);if (!isValidSchemeChar(i, c)) {return null;}}return spec.substring(0, colon).toLowerCase(Locale.US);}

public static string getSchemePrefix(string spec){int colon = spec.IndexOf(':');if (colon < 1){return null;}{for (int i = 0; i < colon; i++){char c = spec[i];if (!isValidSchemeChar(i, c)){return null;}}}return Sharpen.StringHelper.Substring(spec, 0, colon).ToLower(System.Globalization.CultureInfo.InvariantCulture);}
