After learning the basics of LINQ in part 1 of this book and gaining knowledge of in-memory LINQ queries in part 2, it's time to have a break before discovering other LINQ variants. You've already learned a lot about LINQ queries and in particular about LINQ to Objects in chapter 4. You may think that this is enough to write efficient LINQ queries. Think again. LINQ is like an ocean where each variant is an island. We have taught you the rudiments of swimming, but you need to learn more before you can travel safely to all the islands. You know how to write a query, but do you know how to write an efficient query? In this chapter, we'll expand on some of our earlier ideas to improve your skills of LINQ. We're going to step back and look at how to make the most of what we've covered so far.