Programatically download file from document library.

You probably have this kind of scenario, you have developed a document library system base on the WSS object model, users of this system need to download files from backend WSS site, but sometimes these users can't access the backend WSS site, you just grant the proper permission to them in your system, I mean they are probably the reader to your system, but not the reader to backend WSS site. So if they want to download files, you can't just give them a specific URL(eg. http://HostName/sites/LibName/ListName/FileName.doc").

Obviously, you need to solve this problem, okay, here is the code:

///   <summary>
///  Used for downloading files from DocLib
///   </summary>
public   class  SPSFileDownloader
{
     string  m_FileUrl;
     string  m_FileName;
    NetworkCredential m_NetworkCredential;

     ///   <summary>
     ///  Constructor
     ///   </summary>
     ///   <param name="fileUrl"> File URL( http://HostName/sites/LibName/ListName/FileName.doc ) </param>
     ///   <param name="fileName"> File Name </param>
     ///   <param name="networkCredential"> Credential </param>
     public  SPSFileDownloader( string  fileUrl,  string  fileName, NetworkCredential networkCredential)
    {
         this .m_FileName  =  fileName;
         this .m_FileUrl  =  fileUrl;
         this .m_NetworkCredential  =  networkCredential;
    }

     public   void  Download()
    {
        HttpWebRequest httpWebRequest  =     (HttpWebRequest) WebRequest.Create( this .m_FileUrl);
        WebHeaderCollection whc  =   new  WebHeaderCollection();
        whc.Add( " Translate " ,  " f " );
        httpWebRequest.Headers  =  whc;

        CredentialCache creCache  =   new  CredentialCache();
        creCache.Add(  new  Uri( this .m_FileUrl),  " NTLM " ,  this .m_NetworkCredential);

        httpWebRequest.Credentials  =  creCache;

        HttpWebResponse httpWebResponse  =  (HttpWebResponse)httpWebRequest.GetResponse();

        Stream responseStream  =  httpWebResponse.GetResponseStream();
         long  fileLength  =  httpWebResponse.ContentLength;
         string  fileName  =  HttpUtility.UrlPathEncode( this .m_FileName);

        HttpContext.Current.Response.Clear();
        HttpContext.Current.Response.AddHeader( " content-disposition " , " attachment;filename= " + fileName);
        HttpContext.Current.Response.ContentType  = " application/octet-stream " ;
        HttpContext.Current.Response.AddHeader( " Content-Length " , fileLength.ToString());
        HttpContext.Current.Response.Buffer  =   true ;

         int  streamPosition  =   1 ;
         byte [] inBuf  =   new  Byte[ 1024 ];
         while  (streamPosition  >   0 ) 
        {
            streamPosition  =  responseStream.Read(inBuf,  0 , inBuf.Length);
            HttpContext.Current.Response.OutputStream.Write(inBuf,  0 , streamPosition);
            HttpContext.Current.Response.Flush();
        }

        responseStream.Close();
        HttpContext.Current.Response.End();
    }
}

Another approach should be "SPFile. OpenBinary()"

Hope this helps.