title: Add comma sequentially to string in C#
body: <p>I have a <strong>string</strong>.</p>
  
  <pre><code>string str = "TTFTTFFTTTTF";
  </code></pre>
  
  <p>How can I break this string and add character ","?</p>
  
  <pre><code>result should be- TTF,TTF,FTT,TTF
  </code></pre>