ASP.net實現文件下載

方式一：TransmitFile實現下載。將指定的文件直接寫入 HTTP 響應輸出流，而不在內存中緩衝該文件。

    protected void Button1_Click(object sender, EventArgs e)
     ...{
        /**//*
           微軟爲Response對象提供了一個新的方法TransmitFile來解決使用Response.BinaryWrite下載超過400mb的文件時導致Aspnet_wp.exe進程回收而無法成功下載的問題。
     代碼如下：
    */
          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實現下載，將指定的文件直接寫入 HTTP 響應輸出流。注意：對大型文件使用此方法時，調用此方法可能導致異常。可以使用此方法的文件大小取決於 Web 服務器的硬件配置。

    protected void Button2_Click(object sender, EventArgs e)
    ...{
        string fileName = "CodeShark.zip";//客戶端保存的文件名
    string filePath = Server.MapPath("DownLoad/CodeShark.doc");//路徑
     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分塊下載

    protected void Button3_Click(object sender, EventArgs e)
    ...{
        string fileName = "CodeShark.zip";//客戶端保存的文件名
    string filePath = Server.MapPath("DownLoad/CodeShark.zip");//路徑
    System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);
        if (fileInfo.Exists == true)
        ...{
            const long ChunkSize = 102400;//100K 每次讀取文件，只讀取100Ｋ，這樣可以緩解服務器的壓力
      byte[] buffer = new byte[ChunkSize];
             Response.Clear();
             System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
            long dataLengthToRead = iStream.Length;//獲取下載的文件總大小
       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));//讀取的大小
         Response.OutputStream.Write(buffer, 0, lengthRead);
                 Response.Flush();
                 dataLengthToRead = dataLengthToRead - lengthRead;
             }
             Response.Close();
         }
     }

方式四：流方式下載

    protected void Button4_Click(object sender, EventArgs e)
    ...{
        string fileName = "CodeShark.zip";//客戶端保存的文件名
    string filePath = Server.MapPath("DownLoad/CodeShark.zip");//路徑
    //以字符流的形式下載文件
     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";
        //通知瀏覽器下載文件而不是打開
     Response.AddHeader("Content-Disposition", "attachment;    filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
         Response.BinaryWrite(bytes);
         Response.Flush();
         Response.End();
     }

第一個方法我測試過，沒問題，但是我沒有測試超過400MB的內容。其餘三個方法我自己沒具體測試。