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POUsing HttpWebRequest with dynamic URI causes "parameter is not valid" in Image.FromStream
 

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  1. POUsing HttpWebRequest with dynamic URI causes "parameter is not valid" in Image.FromStream
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    <p>I'm trying to obtain an image to encode to a WordML document. The original version of this function used files, but I needed to change it to get images created on the fly with an aspx page. I've adapted the code to use HttpWebRequest instead of a WebClient. The problem is that I don't think the page request is getting resolved and so the image stream is invalid, generating the error "parameter is not valid" when I invoke Image.FromStream.</p> <pre><code> public string RenderCitationTableImage(string citation_table_id) { string image_content = ""; string _strBaseURL = String.Format("http://{0}", HttpContext.Current.Request.Url.GetComponents(UriComponents.HostAndPort, UriFormat.Unescaped)); string _strPageURL = String.Format("{0}{1}", _strBaseURL, ResolveUrl("~/Publication/render_citation_chart.aspx")); string _staticURL = String.Format("{0}{1}", _strBaseURL, ResolveUrl("~/Images/table.gif")); string _fullURL = String.Format("{0}?publication_id={1}&amp;citation_table_layout_id={2}", _strPageURL, publication_id, citation_table_id); try { HttpWebRequest request = (HttpWebRequest)WebRequest.Create(_fullURL); HttpWebResponse response = (HttpWebResponse)request.GetResponse(); Stream image_stream = response.GetResponseStream(); // Read the image data MemoryStream ms = new MemoryStream(); int num_read; byte[] crlf = System.Text.Encoding.Default.GetBytes("\r\n"); byte[] buffer = new byte[1024]; for (num_read = image_stream.Read(buffer, 0, 1024); num_read &gt; 0; num_read = image_stream.Read(buffer, 0, 1024)) { ms.Write(buffer, 0, num_read); } // Base 64 Encode the image data byte[] image_bytes = ms.ToArray(); string encodedImage = Convert.ToBase64String(image_bytes); ms.Position = 0; System.Drawing.Image image_original = System.Drawing.Image.FromStream(ms); // &lt;---error here: parameter is not valid image_stream.Close(); image_content = string.Format("&lt;w:p&gt;{4}&lt;w:r&gt;&lt;w:pict&gt;&lt;w:binData w:name=\"wordml://{0}\"&gt;{1}&lt;/w:binData&gt;" + "&lt;v:shape style=\"width:{2}px;height:{3}px\"&gt;" + "&lt;v:imagedata src=\"wordml://{0}\"/&gt;" + "&lt;/v:shape&gt;" + "&lt;/w:pict&gt;&lt;/w:r&gt;&lt;/w:p&gt;", _word_image_id, encodedImage, 800, 400, alignment.center); image_content = "&lt;w:br w:type=\"text-wrapping\"/&gt;" + image_content + "&lt;w:br w:type=\"text-wrapping\"/&gt;"; } catch (Exception ex) { return ex.ToString(); } return image_content; </code></pre> <p>Using a static URI it works fine. If I replace "staticURL" with "fullURL" in the WebRequest.Create method I get the error. Any ideas as to why the page request doesn't fully resolve?</p> <p>And yes, the full URL resolves fine and shows an image if I post it in the address bar. </p>
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    1. USDan Bailiff
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    1. COSo your `staticURL` refers to file in GIF format. What does `fullURL` refer to? Maybe not a valid image format?
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    2. COWhat error are you getting back? Are you sure that HttpWebRequest is using the exact same Url that you pasted in the browser? Try getting a tracelog with your HttpWebRequest app ( http://ferozedaud.blogspot.com/2009/08/tracing-with-systemnet.html ) and see what it says.
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      1. USferoze
    3. COUsing a StreamReader, I was able to determine that what was being included in the response was the default login page for the user. Seems like some kind of permission issue, but I would have thought that WebRequests would use the permissions given by the user that is already logged in? Anyone have insight to this?
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      1. USDan Bailiff
 

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