title: Extract string that contains only letters in C#
body: <pre><code> string input = "5991 Duncan Road";
   var onlyLetters = new String(input.Where(Char.IsLetter).ToArray());
  </code></pre>
  
  <p><strong>Output: DuncanRoad</strong></p>
  
  <p>But I am expecting output is <strong>Duncan Road</strong>. What need to change ?</p>