title: ArgumentOutOfRangeException when converting UTF-32 (HEX) to string
body: <p>I'm having trouble converting some of the UTF-32 HEX to string. I'm getting this error message</p>
  
  <blockquote>
    <p>"A valid UTF32 value is between 0x000000 and 0x10ffff, inclusive, and
    should not include surrogate codepoint values (0x00d800 ~ 0x00dfff).
    Parameter name: utf32"</p>
  </blockquote>
  
  <p>when using this code</p>
  
  <pre><code>int decodedInt = Convert.ToInt32("D8F5", 16);
  string decodedStr = char.ConvertFromUtf32(decodedInt);
  </code></pre>
  
  <p>when I use this HEX "9FDB", it works without any issues. What am I doing wrong?</p>