title: Keep list of separated marks from string
body: <p>I'm trying to figure out with <code>linq</code> and <code>regex</code> method, to remove all alphabetic and numeric characters and keep only punctuation marks in string:</p>
  
  <pre><code>   string input = ": hello; world; 2019&gt;how?.are,you. .i'm good}and-you[?ok";
  </code></pre>
  
  <p>to  split in output list for each mark not divided by char or number in same string: </p>
  
  <pre><code>:
  ;
  ;
  &gt;
  ?.
  ,
  ..
  '
  }
  -
  [?
  </code></pre>
  
  <p>Any guide or example would be helpful</p>