LINQ GroupBy: The Operator Everyone Uses Wrong GroupBy in LINQ looks like SQL GROUP BY . It isn't. At least, not in the way you'd expect. When you grasp the difference, you stop fighting the operator and start wielding it. The SQL Mental Model (That Misleads You) In SQL, GROUP BY collapses rows into aggregates: SELECT CategoryId , COUNT ( * ) as Count , AVG ( Price ) as AvgPrice FROM Products GROUP BY CategoryId Result...