web开发下的各种下载方法

傷城~ 2021-11-16 09:28 329阅读 0赞

利用TransmitFile方法，解决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);

IO的WriteFile实现下载

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

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

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();

最后一种支持断点下载

/// <summary>
            /// 支持断点续传的下载大文件的函数
            /// </summary>
            /// <param name="downloadFilePath">被下载文件的路径，相对和绝对都可以</param>
            /// <param name="showFileName">显示给用户的文件名，可以为空</param>
            /// <param name="fileType">要下载的文件类型，如果不确定，请留空</param>
            /// <remarks>用于大文件的下载</remarks>
            public static void BigFileDownload(string downloadFilePath, string showFileName, string fileType)
            {
                downloadFilePath = downloadFilePath.Trim();
                if(string.Empty == downloadFilePath)
                    ShowErrorMessage("没有指定要下载的文件路径！");
                
                if(downloadFilePath.IndexOf(":") < 0)
                    downloadFilePath = System.Web.HttpContext.Current.Server.MapPath(downloadFilePath);
    
                showFileName = showFileName.Trim();
                if(string.Empty == showFileName)
                    showFileName = Path.GetFileName(downloadFilePath);
    
                showFileName = System.Web.HttpUtility.UrlEncode(System.Web.HttpContext.Current.Request.ContentEncoding.GetBytes(showFileName));
                
                fileType = fileType.Trim();
                if(string.Empty == fileType)
                    fileType = "application/octet-stream";
    
                System.Web.HttpContext.Current.Response.Clear();
                Stream objStream = null;
                byte[] btBuffer = new byte[8192];  // 1024*8 = 8Kb
                int intLength = 0;
                long lngData2Read = 0;
                try
                {
                    using(objStream = new FileStream(downloadFilePath, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        lngData2Read = objStream.Length;
                        
                        输出HTTP头信息
                        
                        while(lngData2Read > 0)
                        {
                            if(HttpContext.Current.Response.IsClientConnected)
                            {
                                intLength = objStream.Read(btBuffer, 0, 8192);
                                HttpContext.Current.Response.OutputStream.Write(btBuffer, 0, intLength);
                                HttpContext.Current.Response.Flush();
                                lngData2Read -= intLength;
                                btBuffer = new byte[8192];
                            }
                            else
                            {
                                lngData2Read = -1;
                            }
                        }
                    }
                }
                catch(Exception ex)
                {
                    ShowErrorMessage(ex.Message);
                }
                // 结束文件下载，此句不可缺少，否则会把本页的HTML代码一起下载文件里
                HttpContext.Current.Response.End();
            }
    
            /// <summary>
            /// 输出错误信息给用户，采用客户端弹出框的方式
            /// </summary>
            /// <param name="errorMessage">错误信息的内容</param>
            internal static void ShowErrorMessage(string errorMessage)
            {
                errorMessage = errorMessage.Replace("'", "\"");
                System.Web.HttpContext.Current.Response.Write("<script language='javascript'>");
                System.Web.HttpContext.Current.Response.Write("alert('");
                System.Web.HttpContext.Current.Response.Write(errorMessage);
                System.Web.HttpContext.Current.Response.Write("');</script>");
                System.Web.HttpContext.Current.Response.End();
            }