How to group join with multiple collections?

Short answer: How to group join with multiple collections?

Explain a bit more

var groupJoin = from d in departments join e in employees on d.Name equals e.Department into empGroup select new { Department = d.Name, Employees = empGroup }; foreach (var group in groupJoin) Console.WriteLine($"{group.Department}:"); foreach (var emp in group.Employees) Console.WriteLine($" - {emp.Name}"); Follow : Explanation: Groups employees under their respective departments.

Real-world example (ShopNest)

A sales report joins orders and customers, then GroupBy(c => c.City) to show revenue per city.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.