Use let to simplify nested calculation let tax = e.Salary * 0.1?

Short answer: var taxResult = from e in employees select new { e.Name, Tax = tax }; let stores computed value for reuse.

Example code

var taxResult = from e in employees
select new { e.Name, Tax = tax }; let stores computed value for reuse.

Real-world example (ShopNest)

ShopNest uses LINQ to query orders: filter by date, project to a summary DTO, and order by total—readable C# that becomes SQL under EF Core.

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.