How to perform union of two collections without duplicates?

Short answer: How to perform union of two collections without duplicates? var list1 = new[] { "Alice", "Bob", "Charlie" }; var list2 = new[] { "Bob", "David", "Eva" }; var union = list1.Union(list2); foreach (var name in union) Console.WriteLine(name); Explanation: Union returns distinct elements from both collections.

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.