title: Find duplicate items in csv file
body: <p>I have a CSV file  with</p>
  
  <blockquote>
    <p>FirstName LastName and ID column, Id is an Unique Column</p>
  </blockquote>
  
  <pre><code>Chris, Webber, 1 
  Chris, Ben, 2
  Chris, Dudley, 3
  David, Floy, 4
  Chris, Ben, 5 
  Chris, Webber, 6
  </code></pre>
  
  <p>I need to get two list without using a DB, i need to read it from file in c# and create two list duplicate list and originalList.</p>
  
  <p>duplicate list has all the duplicates  entry</p>
  
  <pre><code>Chris, Webber, 1
  Chris, Webber, 6
  Chris, Ben, 2
  Chris, Ben, 5
  </code></pre>
  
  <p>Original List has unique entry and first occurrence of duplicate entry.</p>
  
  <pre><code>Chris, Webber, 1
  Chris, Ben, 2
  Chris, Dudley, 3
  David, Floy, 4
  </code></pre>
  
  <blockquote>
    <p>What is the best way solve this?</p>
  </blockquote>