C# FileStream复制大文件功能

public static class FileHelper  {    /// <summary>    /// 复制大文件    /// </summary>    /// <param name="fromPath">源文件的路径</param>    /// <param name="toPath">文件保存的路径</param>    /// <param name="eachReadLength">每次读取的长度</param>    /// <returns>是否复制成功</returns>    public static bool CopyFile(string fromPath, string toPath, int eachReadLength)    {      //将源文件 读取成文件流      FileStream fromFile = new FileStream(fromPath, FileMode.Open, FileAccess.Read);      //已追加的方式 写入文件流      FileStream toFile = new FileStream(toPath, FileMode.Append, FileAccess.Write);      //实际读取的文件长度      int toCopyLength = 0;      //如果每次读取的长度小于 源文件的长度 分段读取      if (eachReadLength < fromFile.Length)      {        byte[] buffer = new byte[eachReadLength];        long copied = 0;        while (copied <= fromFile.Length - eachReadLength)        {          toCopyLength = fromFile.Read(buffer, 0, eachReadLength);          fromFile.Flush();          toFile.Write(buffer, 0, eachReadLength);          toFile.Flush();          //流的当前位置          toFile.Position = fromFile.Position;          copied += toCopyLength;        }        int left = (int)(fromFile.Length - copied);        toCopyLength = fromFile.Read(buffer, 0, left);        fromFile.Flush();        toFile.Write(buffer, 0, left);        toFile.Flush();       }      else      {        //如果每次拷贝的文件长度大于源文件的长度 则将实际文件长度直接拷贝        byte[] buffer = new byte[fromFile.Length];        fromFile.Read(buffer, 0, buffer.Length);        fromFile.Flush();        toFile.Write(buffer, 0, buffer.Length);        toFile.Flush();       }      fromFile.Close();      toFile.Close();      return true;    }  }

class Program  {    static void Main(string[] args)    {       Stopwatch watch = new Stopwatch();      watch.Start();      if (FileHelper.CopyFile(@"D:/安装文件/新建文件夹/SQLSVRENT_2008R2_CHS.iso", @"F:/SQLSVRENT_2008R2_CHS.iso", 1024 * 1024 * 5))      {        watch.Stop();        Console.WriteLine("拷贝完成,耗时：" + watch.Elapsed.Seconds + "秒");      }      Console.Read();    }  }