"Server cannot append header after HTTP headers have been sent " in multiple file download

Hope this is the right forum!

I have some simple file download code to serve up a file for the user to download - it works fine.

But if I try to server up 2 files by calling the code teice it blows up with the error above right where it would create the "open, Save" dialog

I tried to look for some response properties that would tell me the first download was not finished yet but did not see any.

How can I serve up multiple files for download?

Here is my code:

Response.ContentType = "application/X-unknown"
Response.AddHeader("Content-Disposition", "attachment; filename=""" & myFileName & """")

            Response.TransmitFile(Folderpath & myFileName)
            Response.Flush()
            Response.Close()

Thanks

Bill

Re: "Server cannot append header after HTTP headers have been sent " in multiple file download

Due to the limitations of the http protocol, you can only send one file per request. Therefore, you will need to pack the separate files into one package (zip, for example) and send that. Something like this should help get you started: http://weblogs.asp.net/dneimke/archive/2005/02/25/380273.aspx

Re: "Server cannot append header after HTTP headers have been sent " in multiple file download

Are you sure?

If I could tell that the first download had not finished then I could wait until serving up the next file.

somehting like

while response.someproperty = true then

sleep (1000)

loop

or, if there was a way to specify multiple attachments then I could do them all at once.

something like Response.AddHeader(anotherfile)

I really don't want to send a zip unless I have to

Re: "Server cannot append header after HTTP headers have been sent " in multiple file download

You could try a Response.Redirect back to the same page after each download (after Response.Flush), perhaps passing in a querystring value to determine which file should be next. I've not tried this, but it might work.

Server cannot append header after HTTP headers have been sent

I am getting an error, Server cannot append header after HTTP headers have been sent.
I am trying to download a file from ftp server. I have a grid which displays the list and when the user selects one, I open a pop-up where the download occurs in page_load().It is working fine but when I try to show an image while the download process is going on , I get the above mentioned error.
/*****************Code for image display**************************/
const string MAIN_IMAGE = "/_layouts/images/novartis/waiting.gif";
const int PROGRESS_BAR_SIZE = 10; //number of steps in your progress bar
const string PROGRESS_BAR_STEP = "/_layouts/images/novartis/pik.gif"; //image for idle steps
const string PROGRESS_BAR_ACTIVE_STEP = "/_layouts/images/novartis/pik.gif"; //image for active step
Response.Write("<div id=\"mydiv\" align=\"center\">");
Response.Write("<img src=\"" + MAIN_IMAGE + "\">");
Response.Write("<div id=\"mydiv2\" align=\"center\">");
for (int i = 1; i <= PROGRESS_BAR_SIZE; i++)
{
Response.Write("<img id='pro" + i.ToString() + "' src='" + PROGRESS_BAR_STEP + "'> ");
}
Response.Write("</div>");
Response.Write("</div>");
Response.Write("<script language=javascript>");
Response.Write("var counter=1;var countermax = " + PROGRESS_BAR_SIZE + ";function ShowWait()");
Response.Write("{ document.getElementById('pro' + counter).setAttribute(\"src\",\"" + PROGRESS_BAR_ACTIVE_STEP + "\"); if (counter == 1) document.getElementById('pro' + countermax).setAttribute(\"src\",\"" + PROGRESS_BAR_STEP + "\");else {var x=counter - 1; document.getElementById('pro' + x).setAttribute(\"src\",\"" + PROGRESS_BAR_STEP + "\");} counter++;if (counter > countermax) counter=1;}");
Response.Write("function Start_Wait(){mydiv.style.visibility = \"visible\";window.setInterval(\"ShowWait()\",1000);}");
Response.Write("function Stop_Wait(){ mydiv.style.visibility = \"hidden\";window.clearInterval();}");
Response.Write("Start_Wait();</script>");
Response.Flush();

/**************Code for download**********************/

if (Request.QueryString["DownloadUrl"] != null)
{
FtpWebRequest reqFTP;
//HtmlControl frame1 = (HtmlControl)this.FindControl("frame1");
//frame1.Attributes["src"] = "Iframe1WebForm.aspx";
try
{
string fileName = Request.QueryString["DownloadUrl"].ToString();
string filename = Path.GetFileName(fileName);
WriteLog(filename);
Response.Buffer = true;
Response.Clear();
Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
Response.ContentType = "application/octet-stream";
////Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
Response.Flush();
reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + filename));
WriteLog(reqFTP.RequestUri.ToString());
reqFTP.Proxy = null;
reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
reqFTP.UseBinary = true;
reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword, ftpDomain);
//WebResponse aa = reqFTP.GetResponse();
FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
Stream ftpStream = response.GetResponseStream();
MemoryStream MemStream = new MemoryStream();
int bufferSize = 102400;//2048;
byte[] respBuffer = new byte[bufferSize];
try
{
int bytesRead = ftpStream.Read(respBuffer, 0, respBuffer.Length);
WriteLog("byteRead" + " " + bytesRead.ToString());
while (bytesRead > 0)
{
MemStream.Write(respBuffer, 0, bytesRead);
bytesRead = ftpStream.Read(respBuffer, 0, respBuffer.Length);
WriteLog("inside while" + bytesRead.ToString());
}
byte[] finalByte = MemStream.GetBuffer();
Response.BinaryWrite(finalByte);
}
finally
{
ftpStream.Close();
response.Close();
}
}
catch (Exception ex)
{
throw ex;
}