大文件拷贝原理：向内存申请1M空间，反复从源文件读取1M内容写入到目标文件，直到读完。

 1 private void CopyBigFile() 2  { 3 string originalPath = @"E:\AdvanceCSharpProject\LearnCSharp\21.zip"; 4 string destPath = @"F:\BaiduNetdiskDownload\21.zip"; 5 //定义读文件流 6 using (FileStream fsr = new FileStream(originalPath, FileMode.Open)) 7  { 8 //定义写文件流 9 using (FileStream fsw = new FileStream(destPath, FileMode.OpenOrCreate))10  {11 //申请1M内存空间12 byte[] buffer = new byte[1024 * 1024];13 //无限循环中反复读写，直到读完写完14 while(true)15  {16 int readCount = fsr.Read(buffer, 0, buffer.Length);17 fsw.Write(buffer, 0, readCount);18 if(readCount < buffer.Length)19  {20 break;21  }22  }23  }24  }25 }