断点续传下载功能

public static bool ResponseFile( System.Web.HttpRequest _Request,
           System.Web.HttpResponse _Response,
           string _fileName,string _fullPath, long _speed)
  {
   try
   {
    FileStream myFile = new FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
    BinaryReader br = new BinaryReader(myFile);
    try
    {
     _Response.AddHeader("Accept-Ranges", "bytes");
     _Response.Buffer = false;
     long fileLength = myFile.Length;
     long startBytes = 0;
     
     int pack = 10240; //10K bytes
     if (_Request.Headers["Range"] != null)
     {
      _Response.StatusCode = 206;
      string[] range = _Request.Headers["Range"].Split(new char[] {'=', '-'});
      startBytes = Convert.ToInt64(range[1]);
     }
     _Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
     if (startBytes != 0)
     {
      _Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength-1, fileLength));
     }
     _Response.AddHeader("Connection", "Keep-Alive");
     _Response.ContentType = "application/octet-stream";
     _Response.AddHeader("Content-Disposition","attachment;filename=" + System.Web.HttpUtility.UrlEncode(_fileName,System.Text.Encoding.UTF8) );
     
     br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
     int maxCount = (int) Math.Floor((fileLength - startBytes) / pack) + 1;
     byte[] buffer=new byte[pack];
                                                   
     for (int i = 0; i < maxCount; i++)
     {
      if (_Response.IsClientConnected)
      {
       buffer=br.ReadBytes(pack);
       _Response.OutputStream.Write(buffer, 0, pack);
       _Response.Flush();
       buffer=new byte[pack];
       
      }
      else
      {
       i=maxCount;
      }
     }
    }
    catch(Exception myerror)
    {
     throw myerror;
    }
    finally
    {
     br.Close();
     myFile.Close();
    }
   }
   catch(Exception myerror)
   {
    throw myerror;
   }
   return true;
  }