Dec2Hex.cs

using System;

class Program
{
    static void Main()
    {
        long num = 2882400063;
        string result = "";
        while  (num > 0)
        {
            long d = num % 16;
            result = GetHexDigit(d) + result;
            num = num / 16;
        }
        Console.WriteLine(result);
    }

    private static string GetHexDigit(long d)
    {
        if (d < 10)
            return "" + d;
        else if (d == 10)
            return "A";
        else if (d == 11)
            return "B";
        else if (d == 12)
            return "C";
        else if (d == 13)
            return "D";
        else if (d == 14)
            return "E";
        else if (d == 15)
            return "F";
        else
            throw new Exception("Invalid digit");
    }
}