How to group by multiple keys?

Short answer: How to group by multiple keys? var groupedMulti = employees .GroupBy(e => new { e.Department, SalaryLevel = e.Salary > 75000 ? How to group by multiple keys? var groupedMulti = employees .GroupBy(e => new { e.Department, SalaryLevel = e.Salary > 75000 ? "High" : "Low" }); foreach (var group in groupedMulti) Console.WriteLine($"{group.Key.Department} -…… {group.Key.SalaryLevel} ({group.Count()} employees)"); How to…

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.