title: Fastest way to implement Duplicate Character Removal in String (C#)
body: <p>In C#, what is the fastest way to detect duplicate characters in a String and remove them (removal <strong>including 1st instance</strong> of the duplicated character)?</p>
  
  <p>Example Input: <code>nbHHkRvrXbvkn</code></p>
  
  <p>Example Output: <code>RrX</code></p>