title: Add alternative text for an image in Tagged PDF in C#
body: <p>I need your help with this:</p>
  
  <pre><code>public void manipulatePdf(String src, String dest)
      throws IOException, DocumentException {
      PdfReader reader = new PdfReader(src);
      PdfDictionary catalog = reader.getCatalog();
      PdfDictionary structTreeRoot =
          catalog.getAsDict(PdfName.STRUCTTREEROOT);
      manipulate(structTreeRoot);
      PdfStamper stamper = new PdfStamper(
          reader, new FileOutputStream(dest));
      stamper.close();
  }
  
  public void manipulate(PdfDictionary element) {
      if (element == null)
          return;
      if (PdfName.FIGURE.equals(element.get(PdfName.S))) {
          element.put(PdfName.ALT,
              new PdfString("Figure without an Alt description"));
      }
      PdfArray kids = element.getAsArray(PdfName.K);
      if (kids == null) return;
      for (int i = 0; i &lt; kids.size(); i++)
          manipulate(kids.getAsDict(i));
  }
  </code></pre>
  
  <p>I can port this Java example to C#:</p>
  
  <p>Get the root dictionary from the PdfReader object,
  Get the root of the structure tree (a dictionary),
  Loop over all the kids of every branch of that tree,
  When a lead is a figure, add an /Alt entry.
  Once this is done, use PdfStamper to save the altered file.</p>
  
  <p>But how could I do it? </p>
  
  <p>Could you help me please?</p>
  
  <p>Thank's!</p>