C# Atomic File Write Sample

program.cs

using System;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace AtomicWriteSample
{
    class Program
    {
        static void Main(string[] args)
        {
            string filePath = Path.Combine(Path.GetTempPath(), "foo.txt");
            Parallel.For(0, 10, new ParallelOptions() { MaxDegreeOfParallelism = 10 }, i =>
            {
                byte[] fileContent = Encoding.UTF8.GetBytes("hello there: " + i.ToString());
                using (Stream stream = new MemoryStream(fileContent))
                {
                    try
                    {
                        WriteFile(filePath, stream);
                        Console.WriteLine("Winner: " + i.ToString() + ", ThreadId: " + Thread.CurrentThread.ManagedThreadId);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine(ex.Message + ": " + i.ToString() + ", ThreadId: " + Thread.CurrentThread.ManagedThreadId);
                    }
                }
            });

            Console.ReadLine();
        }

        static void WriteFile(string filePath, Stream fileStream)
        {
            string tempFilePath = Path.GetTempFileName();
            using (FileStream tempFile = File.OpenWrite(tempFilePath))
            {
                fileStream.CopyTo(tempFile);
            }

            try
            {
                File.Move(tempFilePath, filePath);
            }
            catch (Exception ex)
            {
                try
                {
                    File.Delete(tempFilePath);
                }
                catch (Exception)
                {
                    Console.WriteLine("cannot delete as well!!!");
                }

                throw;
            }
        }
    }
}