title: extract substring after the first underscore
body: <p>I need to remove the underscore and all characters before it in my filename.  The syntax of the filename is as follows:</p>
  
  <pre><code>&lt;username&gt;_&lt;NameofFile&gt;_&lt;InstructorName&gt;_&lt;ClassName&gt;.xls  
  </code></pre>
  
  <p>I want to keep everything BUT the <code>&lt;username&gt;_</code> part.<br>
  I tried using <code>.Split</code> as follows:</p>
  
  <pre><code>string newfilename = file.Split('_')[1];
  </code></pre>
  
  <p>but that dropped everything and only kept <code>&lt;NameOfFile&gt;</code>.<br>
  How could this be achieved?</p>