title: PLINQ not improving the performance
body: <p>I wrote a LINQ to find out frequencies of unique characters from a text file.I was also transforming my initial result into an object with the help of select.The final result comes out in the form of a List.
  Below is the query i have used. </p>
  
  <pre><code>charNodes = inputString.GroupBy(ch =&gt; ch)
              .Select((ch) =&gt; new TNode(ch.Key.ToString(),ch.Count()))
              .ToList&lt;TNode&gt;();
  </code></pre>
  
  <p>I have a quad core machine running and the above query ran in 15ms.But strangely it took more time when i PLINQ'ed the same query.The below one took about 40ms.</p>
  
  <pre><code>charNodes = inputString.GroupBy(ch =&gt; ch).AsParallel
              .Select((ch) =&gt; new TNode(ch.Key.ToString(),ch.Count()))
              .ToList&lt;TNode&gt;();
  </code></pre>
  
  <p>Worst was the case with the next query that took about 83ms</p>
  
  <pre><code>charNodes = inputString.AsParallel().GroupBy(ch =&gt; ch)
                                 .Select((ch) =&gt; new TNode(ch.Key.ToString(), ch.Count()))
                                 .ToList&lt;TNode&gt;();
  </code></pre>
  
  <p>What is going wrong here?.</p>