using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;
using System.Threading;

namespace StreamWin
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
      string filePaths = @"E:\Test\Test\local\a.txt";
      string fileName ="a.txt" ;

      System.IO.FileInfo f = new FileInfo(@"E:\Test\Test\server\a.txt");
      int fileLength = Convert.ToInt32(f.Length.ToString());

      ThreadPool.SetMaxThreads(100, 100);
      using (System.IO.FileStream stream = new System.IO.FileStream(filePaths, FileMode.Create,FileAccess.Write, FileShare.Write, 1024, true))
      {
        for (int i = 0; i < fileLength; i +=100 * 1024)
        { 
          int length = (int)Math.Min(100 * 1024, fileLength - i);
          var bytes = GetFile(fileName, i, length);
          stream.BeginWrite(bytes, 0, length, new AsyncCallback(Callback), stream);
        }
        stream.Flush();
      }
    }

    public static byte[] GetFile(string name, int start, int length)
    {
      string filepath = @"E:\Test\Test\server\a.txt";
      using (System.IO.FileStream fs = new System.IO.FileStream(filepath, System.IO.FileMode.Open, System.IO.FileAccess.Read, FileShare.ReadWrite,1024,true))
      {
        byte[] buffer = new byte[length];
        fs.Position = start;
        fs.BeginRead(buffer, 0, length,new AsyncCallback(Completed),fs);
        return buffer;
      }
    }

    static void Completed(IAsyncResult result)
    {
      FileStream fs = (FileStream)result.AsyncState;
      fs.EndRead(result);
      fs.Close();
    }
    public static void Callback(IAsyncResult result)
    {
      FileStream stream = (FileStream)result.AsyncState;
      stream.EndWrite(result);
      stream.Close();
    }
  }
}