How can you perform a LINQ query on a collection to filter, sort, or group elements?

Short answer: Filter: Use Where() to select elements based on a condition. Sort: Use OrderBy() or OrderByDescending(). Group: Use GroupBy() to group elements by a key.

Example code

var products = new List<Product> { ... }; // Filter products with price > 100 var expensiveProducts = products.Where(p => p.Price > 100); // Sort products by name var sortedProducts = products.OrderBy(p => p.Name); // Group products by category var groupedProducts = products.GroupBy(p => p.Category);

Real-world example (ShopNest)

In ShopNest checkout, choose the collection by need: List for ordered cart lines, Dictionary for fast SKU lookup, HashSet for unique tags.

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.