APRS passcode generator in C#

callpass.cs

class Program
{
    static void Main(string[] args)
    {
        System.Console.WriteLine(DoHash("mycall"));
    }

    static int DoHash(string call)
    {
        string upper = call.ToUpper();
        string main = upper.Split('-')[0];

        int hash = 0x73e2;

        char[] chars = main.ToCharArray();

        while (chars.Length != 0)
        {
            char? one = shift(ref chars);
            char? two = shift(ref chars);
            hash = hash ^ one.Value << 8;

            if (two != null)
            {
                hash = hash ^ two.Value;
            }
        }

        int result = hash & 0x7fff;

        return result;
    }

    static char? shift(ref char[] chars)
    {
        if (chars.Length == 0)
            return null;

        char result = chars[0];

        char[] newarr = new char[chars.Length - 1];

        for (int i = 1; i < chars.Length; i++)
        {
            newarr[i - 1] = chars[i];
        }

        chars = newarr;

        return result;
    }
}