title: StringBuilder - find last index of a character
body: <p>I'd like to find a specific last character in a <code>StringBuilder</code>.<br>
  I know, I can solve it with <code>while()</code> but is there an build it option to do that easily?</p>
  
  <p>eg:</p>
  
  <pre><code>private static StringBuilder mySb = new StringBuilder("");
  mySb.Add("This is a test[n] I like Orange juice[n] Can you give me some?");
  </code></pre>
  
  <p>Now: It shoud find the <code>]</code> and give me the possition. Like: 40</p>
  
  <p>Thanks in advance</p>