title: iTextSharp checkbox has value but is not visible as checked
body: <p>I need to edit my PDF file using iTextSharp. I have a radio button and checkbox as described below.</p>
  
  <p>I want to have the following: if I put a check mark on the radio button, then the checkbox must be visible as checked.</p>
  
  <p>In the code, the radio button has a value but when I open the PDF file  for the first time, the checkbox is not checked.</p>
  
  <p>When I again put a check mark in the radio button then it turns visible. </p>
  
  <p>Here is my code;</p>
  
  <pre><code>PdfReader pdfReader = new PdfReader(pdfTemplate);
  PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(newFile, FileMode.OpenOrCreate)); 
  AcroFields pdfFormFields = pdfStamper.AcroFields;
  pdfFormFields.SetField("4a.0", "1"); // radio button
  pdfFormFields.SetField("4a.1", "1"); // checkbox
  pdfFormFields.SetField("4a.2", "2010"); // text box 
  </code></pre>