C# FileStream实现大文件复制

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();  }  }