title: Handle Union of List in C# with duplicates
body: <p>I am trying to understand how to handle union or merge of two lists that can have duplicates.
  For example, List1 has { A, B, C} and List2 has { B, C, D }.
  I tried to use the Union operation and got a new list with values (A, B, C, D}. However, I need the B &amp; C values from the second list, not first one.
  Is there a way to specify the union method, which duplicate value to use.</p>
  
  <p>The code I am using now is</p>
  
  <pre><code>var newList = List1.Union&lt;Object&gt;(List2).ToList();
  </code></pre>
  
  <p>Thanks for any help.
  Javid</p>