decimal settings

public static bool HasDecimalComma;
public static bool HasDecimalPeriod;

public static double GetNumber(string NumberString)
{
    if (!HasDecimalComma && !HasDecimalPeriod)
    {
        string s = string.Format("{0:0.0}", 123.123);
        if (s.Contains('.'))
        {
            HasDecimalPeriod = true;
        }
        else if (s.Contains(','))
        {
            HasDecimalComma = true;
        }
        else
        {
            throw new SystemException(string.Format("strange number format '{0}'", s));
        }
    }
    if (HasDecimalComma)
    {
        return double.Parse(NumberString.Replace('.', ','));
    }
    if (HasDecimalPeriod)
    {
        return double.Parse(NumberString.Replace(',', '.'));
    }
    throw new ArgumentException(string.Format("can't parse '{0}'", NumberString));
}