public static bool IsRijksregisternummer(string data) {
    try {
        if (data == null) return false;
        if (data.Length != 11) return false;
        string leftPartS = data.Substring(0,9);
        string rightPartS = data.Substring(9);

        int leftPartI = int.Parse(leftPartS);
        int rightPartI = int.Parse(rightPartS);

        // Special check for children of 21st century
        int year = DateTime.Today.Year - 2000;
        if (leftPartI < year * 10000000) {
            leftPartI += 2000000000;
        }

        int mod = leftPartI % 97;
        int compareTo = 97 - mod;
        return compareTo == rightPartI;
    } catch (ApplicationException) {
        return false;
    }
}