asp.net+C#如何实现下载文件

protected void Button1_Click(object sender, EventArgs e)  {  /*  微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite  下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。  代码如下：  */  Response.ContentType = "application/x-zip-compressed";  Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");  string filename = Server.MapPath("DownLoad/aaa.zip");  Response.TransmitFile(filename);  }  //WriteFile实现下载  protected void Button2_Click(object sender, EventArgs e)  {  /*  using System.IO;  */  string fileName ="aaa.zip";//客户端保存的文件名  string filePath=Server.MapPath("DownLoad/aaa.zip");//路径  FileInfo fileInfo = new FileInfo(filePath);  Response.Clear();  Response.ClearContent();  Response.ClearHeaders();  Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);  Response.AddHeader("Content-Length", fileInfo.Length.ToString());  Response.AddHeader("Content-Transfer-Encoding", "binary");  Response.ContentType = "application/octet-stream";  Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");  Response.WriteFile(fileInfo.FullName);  Response.Flush();  Response.End();  }  //WriteFile分块下载  protected void Button3_Click(object sender, EventArgs e)  {  string fileName = "aaa.zip";//客户端保存的文件名  string filePath = Server.MapPath("DownLoad/aaa.zip");//路径  System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);  if (fileInfo.Exists == true)  {  const long ChunkSize = 102400;//100K 每次读取文件，只读取100Ｋ，这样可以缓解服务器的压力  byte[] buffer = new byte[ChunkSize];  Response.Clear();  System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);  long dataLengthToRead = iStream.Length;//获取下载的文件总大小  Response.ContentType = "application/octet-stream";  Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));  while (dataLengthToRead > 0 && Response.IsClientConnected)   {  int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小  Response.OutputStream.Write(buffer, 0, lengthRead);  Response.Flush();  dataLengthToRead = dataLengthToRead - lengthRead;  }  Response.Close();  }  }  //流方式下载  protected void Button4_Click(object sender, EventArgs e)  {  string fileName = "aaa.zip";//客户端保存的文件名  string filePath = Server.MapPath("DownLoad/aaa.zip");//路径  //以字符流的形式下载文件  FileStream fs = new FileStream(filePath, FileMode.Open);  byte[] bytes = new byte[(int)fs.Length];  fs.Read(bytes, 0, bytes.Length);  fs.Close();  Response.ContentType = "application/octet-stream";  //通知浏览器下载文件而不是打开  Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));  Response.BinaryWrite(bytes);  Response.Flush();  Response.End();  }