I've inherited a legacy application that is supposed to grab an on the fly pdf from a reporting services server. Everything works fine up until the point where you try to open the pdf being returned and adobe acrobat tells you:

Adobe Reader could not open 'thisStoopidReport'.pdf' because it is either not a supported file type or because the file has been damaged(for example, it was sent as an email attachment and wasn't correctly decoded).

I've done some initial troubleshooting on this. If I replace the url in the WebRequest.Create() call with a valid pdf file on my local machine ie: @"C:temp/validpdf.pdf") then I get a valid PDF.

The report itself seems to work fine. If I manually type the URL to the reporting services report that should generate the pdf file I am prompted for user authentication. But after supplying it I get a valid pdf file.

I've replace the actual url,username,userpass and domain strings in the code below with bogus values for obvious reasons.

        WebRequest request = WebRequest.Create(@"http://x.x.x.x/reportServer?/reports/reportNam&rs:format=pdf&rs:command=render&rc:parameters=blahblahblah");
        int totalSize = 0;
        request.Credentials = new NetworkCredential("validUser", "validPass", "validDomain");
        request.Timeout = 360000; // 6 minutes in milliseconds.
        request.Method = WebRequestMethods.Http.Post;
        request.ContentLength = 0;
        WebResponse response = request.GetResponse();
        Response.Clear();
        BinaryReader reader = new BinaryReader(response.GetResponseStream());
        Byte[] buffer = new byte[2048];
        int count = reader.Read(buffer, 0, 2048);
        while (count > 0)
        {
            totalSize += count;
            Response.OutputStream.Write(buffer, 0, count);
            count = reader.Read(buffer, 0, 2048);
        }
        Response.ContentType = "application/pdf";
        Response.Cache.SetCacheability(HttpCacheability.Private);
        Response.CacheControl = "private";
        Response.Expires = 30;
        Response.AddHeader("Content-Disposition", "attachment; filename=thisStoopidReport.pdf");
        Response.AddHeader("Content-Length", totalSize.ToString());
        reader.Close();
        Response.Flush();
        Response.End();