SteamBot - Internal Server Error

using Newtonsoft.Json;
using SteamKit2;
using SteamTrade;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace SteamBot
{
    public class FileWatcher
    {
        private FileSystemWatcher fileSystemWatcher;
        private string FileToWatch = AppDomain.CurrentDomain.SetupInformation.ApplicationBase + "TradeRequests";

        private Bot Bot;
        private Log Log;
        private SteamWeb SteamWeb;

        public FileWatcher(Bot Bot, Log Log, SteamWeb SteamWeb)
        {
            this.Bot = Bot;
            this.Log = Log;
            this.SteamWeb = SteamWeb;
            fileSystemWatcher = new FileSystemWatcher(FileToWatch);
            fileSystemWatcher.EnableRaisingEvents = true;

            // Instruct the file system watcher to call the FileCreated method
            // when there are files created at the folder.
            fileSystemWatcher.Created += new FileSystemEventHandler(FileCreated);
        }

        public void FileCreated(Object Sender, FileSystemEventArgs Event)
        {

            if (Event.Name.StartsWith("Trade-Request-"))
            {
                SteamBot.TradeRequest.TradeRequestOffer Trade = JsonConvert.DeserializeObject<SteamBot.TradeRequest.TradeRequestOffer>(File.ReadAllText(Event.FullPath));
                Console.WriteLine(Trade.SteamID);

                // creating a new trade offer with token
                SteamID TradeUser = new SteamID(Trade.SteamID);
                var TradeOffer = Bot.NewTradeOffer(TradeUser);
                //offer.Items.AddMyItem(0, 0, 0);

                List<long> contextId = new List<long>();
                contextId.Add(2);
                GenericInventory TradeInventory = new GenericInventory(SteamWeb);
                TradeInventory.load(730, contextId, Trade.SteamID);
                List<ulong> itemsWanted = new List<ulong>();
                foreach (int assetId in Trade.ItemIDs)
                {
                    itemsWanted.Add(Convert.ToUInt64(assetId));
                }

                foreach (GenericInventory.Item Item in TradeInventory.items.Values)
                {
                    if (itemsWanted.Contains(Item.assetid)) {
                        TradeOffer.Items.AddTheirItem(730, 2, Convert.ToInt64(Item.assetid));
                        Log.Warn("Added item: " + TradeInventory.getDescription(Item.assetid).name);
                    }
                }
                Log.Warn("Finished adding items...");
                if (TradeOffer.Items.NewVersion)
                {
                    string newOfferId;
                    Log.Warn("Created offer id.");
                    // "token" should be replaced with the actual token from the other user
                    if (TradeOffer.SendWithToken(out newOfferId, Trade.SteamToken))
                    {
                        Log.Success("Trade offer sent : Offer ID " + newOfferId);
                    }
                }


            }

        }
    }
}