Every once in a while you have to dig deep into your application and look for problems! I have a application that wasn't performing! After searching a bit I found my problem: I do a huge amount of queries and then sum some of the fields in these collections using the Sum extension method (System.Linq.Enumerable). This does make the code easier to read but I never realized the performance hit!!! To test this, I wrote a very simple application with a list of employees. class Employee { public int...