asp.net下载文件几种方式

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();

      }