Based on the js version that Emily wrote. This takes a steamid64 and turns it into a CSGO friend code or takes a friend code and turns it into a steamid64.
using System;
namespace CSGOFriendCodeConverter
{
class Program
{
static void Main(string[] args)
{
// Should be SUCVS-FADA
Console.WriteLine(FriendCode.encode("76561197960287930"));
// should be 76561197960287930
Console.WriteLine(FriendCode.decode("SUCVS-FADA"));
//Also implemented other methods from original module, check out https://github.com/emily33901/js-csfriendcode
}
}
}