How to write joins (inner, left) in LINQ with EF Core?

Short answer: Inner join

Example code

var query = from c in context.Customers join o in context.Orders on c.Id equals o.CustomerId select new { c.Name, o.OrderDate }; Left join (using DefaultIfEmpty()): var query = from c in context.Customers join o in context.Orders on c.Id equals o.CustomerId into orders from o in orders.DefaultIfEmpty() select new { c.Name, OrderDate = o != null ? o.OrderDate : (DateTime?)null };

Real-world example (ShopNest)

ShopNest’s order service uses EF Core to save an Order and its line items in one SaveChangesAsync() call inside a transaction.

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.