C#

// List<ProdTotalSales> salesLst
ProdTotalSales ps = salesLst.First(p => p.Month == o.OrderDatum.Month);
ps.Antal += r.BestSaldo;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            FileStream Stream = new FileStream("test.file", FileMode.Create, FileAccess.ReadWrite, FileShare.None);
            int i;
            int NumReads, NumWrites;
            NumReads = 0;
            NumWrites = 0;
            for (i = 0; i < 1024 * 1024; i++)
            {
                Stream.WriteByte(0);
                NumWrites++;
            }
            while (true)
            {
                for (i = 0; i < Stream.Length; i++)
                {
                    Stream.Position = i;
                    int x=Stream.ReadByte();
                    NumReads++;
                    if (i % 16 == 0)
                    {
                        Stream.Position = i + 8;
                        int y = Stream.ReadByte();
                        NumReads++; 
                        Stream.Position = i + 10;
                        Stream.WriteByte(1);
                        NumWrites++;
                    }
                }
                Console.WriteLine("Loop done. Reads="+NumReads.ToString()+", Writes="+NumWrites.ToString());
                ConsoleKeyInfo result = Console.ReadKey();
                if (result.Key==ConsoleKey.Escape) break;
            }
            Stream.Close();
        }
    }
}