public static string SubstringAfter(string s1, string s2)
{
if (s2.Length == 0) { return s1; }
//int idx = collation.IndexOf(s1, s2);
int idx = s_compareInfo.IndexOf(s1, s2, CompareOptions.Ordinal);
return (idx < 0) ? string.Empty : s1.Substring(idx + s2.Length);
}