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Loops that want to be LINQ

A hand-rolled group-and-total. Say what you want instead of how to get it.

Beginner18 min on the clock6 graded checks · 100 pointsC# Foundations

Graded by reading your code against the checklist below.

What you build

Drop the refunded sales before doing any work on them
Group what is left by category
Total each group
Order the result by revenue, highest first
Return a materialised list, not a running dictionary you built by hand

Done means

Same categories, same totals, no += bookkeeping.

How it is graded

Published in full, before you start — every point is one of these and there is nothing else.

Group by category with GroupBy+25LINQ instead of loops
Total each group+20LINQ instead of loops
Project each group into a result shape+20LINQ instead of loops
Filter before you group+15LINQ instead of loops
Let LINQ do the bookkeeping+10LINQ instead of loops
Order the result+10LINQ instead of loops

What it teaches

LINQ instead of loopsbeginner

LINQ lets you say what you want from a collection — filtered, grouped, totalled — instead of writing the bookkeeping loop that does it, which is most of the C# you will read at work.

The rest of C# Foundations

The wrong containerBeginner · 15 min Where null gets inBeginner · 18 min Blocking the threadBeginner · 20 min Types that say what they areBeginner · 18 min Catching what you can handleBeginner · 16 min