title: Linq Query with SUM and ORDER BY
body: <p>I have a (C#) class called Hit with an ItemID (int) and a Score (int) property. I skip the rest of the details to keep it short. Now in my code, I have a huge List on which I need to do the following select (into a new List): I need to get the sum of all Hit.Score's for each individual Hit.ItemID, ordered by Score. So if I have the following items in the original list</p>
  
  <pre><code>ItemID=3, Score=5
  ItemID=1, Score=5
  ItemID=2, Score=5
  ItemID=3, Score=1
  ItemID=1, Score=8
  ItemID=2, Score=10
  </code></pre>
  
  <p>the resulting List should contain the following:</p>
  
  <pre><code>ItemID=2, Score=15
  ItemID=1, Score=13
  ItemID=3, Score=6
  </code></pre>
  
  <p>Can somebody help?</p>