C#でモジュラス43の計算

バーコードのCode39で使うチェックディジットです

private static char[] modulus43CharList =
{
    '0','1','2','3','4','5','6','7','8','9',
    'A','B','C','D','E','F','G','H','I','J',
    'K','L','M','N','O','P','Q','R','S','T',
    'U','V','W','X','Y','Z','-','.',' ','$',
    '/','+','%'
};

/// 

/// モジュラス43　計算
/// CODE39
/// 
public static string GetModulus43(string Value)
{
    if (!Regex.IsMatch(Value, @"^[A-Z|0-9|\-|.| |$|/|+|%]+$"))
    {
        throw new FormatException();
    }

    long x = 0;
    for (int i = 0; i < Value.Length; i++)
    {
        x += Array.IndexOf(modulus43CharList, Value[i]);
    }

    return modulus43CharList[x % 43].ToString();
}