title: Concat and/or merge objects in two generic lists
body: <p>i need help with this problem...
  I have two lists of same objects "SearchResult", this object has an id attribute and a score attribute.
  In both list can exist the same id, but with different score, so i need to create a new List that combines same id's but the score must be the sum of both scores and finally, the list get ordered by that final score.
  How can i do that?
  I search for a linq query, but i cant find any solution.</p>
  
  <p>I hope you can help me, thanks!!! </p>