title: Specify equality with a lambda expression
body: <p>I want to compare 2 collections. One of these is a <code>List&lt;string&gt;</code> and the other is a <code>List&lt;Book&gt;</code>. Book has a Isbn property of type <code>string</code>, and I want write something like that : </p>
  
  <pre><code>List&lt;string&gt; isbnBooks= new List&lt;string&gt; {"978-1933988276", "978-0321146533", "3"};
  List&lt;Book&gt; books = new List&lt;Book&gt;();
  
  books.Add(new Book { Isbn="978-1933988276", Name="The Art of Unit Testing"});
  books.Add(new Book { Isbn="978-0321146533", Name="TDD By Example"});
  books.Add(new Book { Isbn="978-0321503626", Name="Growing Object-Oriented Software"});
  
  // What I want to write
  var intersectedBooks = books.Intersect(books, isbnBooks, (book, isbn) =&gt; book.Isbn == isbn));
  </code></pre>
  
  <p>I would like specify equality in the method. Is it possible ? Or should I mandatory create a BookComparer which implements IEqualityComparer interface ?</p>
  
  <p>Regards, </p>
  
  <p>Florian</p>