.net下载文件

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();
    }