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C# - 文件下载

• 文件分块下载
  
  • 原理
    每次只读取一部分文件流，如100k到缓冲区，使用flush()将缓冲区的内容刷新到文件中。
  • 代码

public void Download(filePath){    filePath=Server.MapPath(filePath);; //要下载的文件路径    string fileName = "downloadfile.txt";//客户端将要保存的文件名                      const long Size = 102400;//缓冲区大小100K ，每次读取文件，只读取100K，缓解服务器的压力      byte[] buffer = new byte[Size];      FileStream stream = null;     try{        stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);//打开文件        Response.Clear();        long fileSize= stream.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 (fileSize> 0 && Response.IsClientConnected)        {             int lengthRead=stream.Read(buffer,0,Convert.ToInt32(Size));//读取的大小              Response.OutputStream.Write(buffer, 0, lengthRead);            Response.Flush();            fileSize= fileSize- lengthRead;        }    }    catch(Exception ex){        Response.Write("下载失败:" + ex.Message);    }    finally{        if (stream != null)        {            stream.Close();        }        Response.Close();    }}

• 从ftp文件服务器上分块下载文件
  
  • 原理
    先从ftp服务器上读取部分文件流到缓冲区，然后再使用flush()函数将缓冲区的文件刷新到文件中。
  • 代码
    FTPHelper中的下载方法

/// <summary>/// 文件下载/// </summary>/// <param name="buffer">缓冲区</param>/// <param name="Size">读取文件大小</param>/// <param name="URIpath">ftp文件路径</param>/// <returns></returns>public int DownLoadFile(byte[] buffer, long Size, string URIpath){     FtpWebRequest ftp;    int lengthRead = 0;    try    {        ftp = (FtpWebRequest)FtpWebRequest.Create(new Uri(URIpath));        ftp.Method = WebRequestMethods.Ftp.DownloadFile;        ftp.UseBinary = true;        ftp.Credentials = new NetworkCredential(ConfigureHelper.getConfigKey("ftpUserName"), ConfigureHelper.getConfigKey("ftpPassword"));        FtpWebResponse response = (FtpWebResponse)ftp.GetResponse();        Stream ftpStream = response.GetResponseStream();        lengthRead = ftpStream.Read(buffer, 0, Convert.ToInt32(Size));        ftpStream.Close();        response.Close();    }    catch (Exception e)    {    }    return lengthRead;} 

controller方法

public void Download(filePath){    string fileName = "downloadfile.txt";//客户端将要保存的文件名                      const long Size = 102400;//缓冲区大小100K ，每次读取文件，只读取100K，缓解服务器的压力      byte[] buffer = new byte[Size];       try{         Response.Clear();        long fileSize= getFileSize();//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 (fileSize > 0 && Response.IsClientConnected)        {             int lengthRead = FTPClientHelper.ftp.DownLoadFile(buffer, Size , filePath);//读取的大小              Response.OutputStream.Write(buffer, 0, lengthRead);            Response.Flush();            fileSize= fileSize- lengthRead;        }    }    catch(Exception ex){        Response.Write("下载失败:" + ex.Message);    }    finally{        Response.Close();    }}