SystemsConvertion algorithm

var hex = "FAB1";
        var decimalRepresent = 0;
        for (int i = 0; i < hex.Length; i++)
            {
                decimalRepresent *= 16;
                if (hex[i] >= '0' && hex[i] <= '9')
                {
                    decimalRepresent += hex[i] - '0';
                }
                else
                {
                    decimalRepresent += hex[i] + 10 - 'A';
                }
            }
        Console.WriteLine(decimalRepresent);