title: convert a hex string to corresponding emoji string
body: <p>I'm trying to create a string with emoji <code>""</code> starting from this string <code>"D83DDC71"</code>. For doing that I'm trying to convert the string above in this string <code>"\uD83D\uDC71"</code>.</p>
  
  <p>If i use this code it work (textbox shows  as expected):</p>
  
  <pre><code>textbox.Text += "\uD83D\uDC71";
  </code></pre>
  
  <p>but if i use this it doesn't work (textbox shows exact text  "\uD83D\uDC71" instead of single character):</p>
  
  <pre><code>textbox.Text += sender.Code.ToString("X").insert(4, @"\u").insert(0, @"\u");
  </code></pre>
  
  <p>What is the right way to convert hex representation of an emoji to a corresponding C# string (UTF-16)?</p>