Stage 2 · Lesson 2 of 6
LINQ: filter, shape, sort and group
(Language Integrated Query) is a set of methods you chain to work with data. Where filters, Select shapes each item into something new, OrderBy sorts, GroupBy buckets, and Sum, Count and Average reduce. First, Single and their OrDefault versions pick one item, and Any checks existence.
The same chain works on a list in memory and on an EF Core , where it becomes SQL, so you learn it once and use it everywhere. Read and write the method syntax, since it is what most codebases use, and be able to read query syntax (from o in orders where ...) in older code.
Common trapcalling ToList() too early: everything after it runs in memory, so you load whole tables to keep five rows.
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Resources for this stage
Start with· follow one of these
- CoursePaidGrokking Data Structures & Algorithms for Coding Interviews
Design Gurus · Beginner · Subscription
Arrays, hash tables, lists, stacks and queues: what every C# collection is built on, with complexity explained
- GuideFree.NET documentation
Microsoft
Free official guides on LINQ, generics, collections and the asynchronous programming model