ASP.NET实现文件下载

方式一：TransmitFile实现下载。将指定的文件直接写入 HTTP 响应输出流，而不在内存中缓冲该文件。

     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=CodeShark.zip " );
          string filename = Server.MapPath( " DownLoad/CodeShark.zip " );
          Response.TransmitFile(filename);
      }

方式二： WriteFile实现下载，将指定的文件直接写入 HTTP 响应输出流。注意：对大型文件使用此方法时，调用此方法可能导致异常。可以使用此方法的文件大小取决于 Web 服务器的硬件配置。

     protected void Button2_Click( object sender, EventArgs e)
     ... {
         string fileName = " CodeShark.zip " ; // 客户端保存的文件名
     string filePath = Server.MapPath( " DownLoad/CodeShark.doc " ); // 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();
     }

方式三：WriteFile分块下载

     protected void Button3_Click( object sender, EventArgs e)
     ... {
         string fileName = " CodeShark.zip " ; // 客户端保存的文件名
     string filePath = Server.MapPath( " DownLoad/CodeShark.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();
         }
     }

方式四：流方式下载

     protected void Button4_Click( object sender, EventArgs e)
     ... {
         string fileName = " CodeShark.zip " ; // 客户端保存的文件名
     string filePath = Server.MapPath( " DownLoad/CodeShark.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();
     }