asp.net中实现文件下载功能

// 1 TransmitFile实现下载
     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 " );//绝对路径为：string path=@"D:\1.jpg";
         Response.TransmitFile(filename);
     }

     //2 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();
     }

     //3 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();
         }
     }

     // 4  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();

     }