SklonenieCSharp.cs

public static string GetNoun(long number, String one, String two, String five)
{
    number = Math.Abs(number);
    number %= 100;
    if (number >= 5 && number <= 20)
    { 
        return five;
    }
    number %= 10;
    if (number == 1)
    {
        return one;
    }
    if (number >= 2 && number <= 4)
    {
        return two;
    }
    return five;
}

public static string GetAdj(long number, String one, String two)
{
    number = Math.Abs(number);
    number %= 100;
    if (number == 11) return two;
    number %= 10;
    if (number == 1) return one;
    return two;
}