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Programming Languages Beginner Bestseller

C# Collections and LINQ: The Cheat-Sheet Course

Pick the right collection and the right LINQ operator every time, in under an hour.

Rated 4.2 out of 5 from 5 reviews 46 students

YT Created by Yuki Tanaka

  • Last updated August 2026
  • English
  • 55m of material
  • 7 lessons

What you will learn

6 concrete outcomes

Every bullet below is something you will have built, shipped or be able to explain by the time you finish the last lesson.

  • Choose between List, Dictionary, HashSet, Queue and Stack from access patterns and costs
  • Know when FrozenDictionary and the immutable collections are worth their construction cost
  • Replace common loops with Where, Select, SelectMany and GroupBy
  • Avoid the First versus FirstOrDefault and Single versus SingleOrDefault mistakes
  • Aggregate data with Sum, Count, Aggregate and ToLookup correctly
  • Keep a one-page reference you will still use months later

Course curriculum

4 modules · 7 lessons · 55m of material

2 lessons running 16m in total. Each lesson ships with the finished source files and a short written recap, so you can follow along in your own editor and skim the module again later.

Lesson-by-lesson titles, code downloads and exercises live inside the course library you get access to straight after checkout.

1 lesson running 8m in total. Each lesson ships with the finished source files and a short written recap, so you can follow along in your own editor and skim the module again later.

Lesson-by-lesson titles, code downloads and exercises live inside the course library you get access to straight after checkout.

3 lessons running 23m in total. Each lesson ships with the finished source files and a short written recap, so you can follow along in your own editor and skim the module again later.

Lesson-by-lesson titles, code downloads and exercises live inside the course library you get access to straight after checkout.

1 lesson running 8m in total. Each lesson ships with the finished source files and a short written recap, so you can follow along in your own editor and skim the module again later.

Lesson-by-lesson titles, code downloads and exercises live inside the course library you get access to straight after checkout.

4 modules · 7 lessons

55m total length

Requirements

Short list, and deliberately so. If you meet these you can start today.

  • Basic C# syntax and the ability to run a console project
  • No prior LINQ experience required

About this course

Every C# codebase has a List where a Dictionary belonged and a foreach loop where a single LINQ call would do. This short course is a reference you work through once and then keep, covering the collection types you should reach for and the query operators that replace hand-written loops.

The first half compares List, Dictionary, HashSet, Queue, Stack and the immutable and frozen variants added in recent .NET releases, with the lookup and insertion costs stated plainly so the choice becomes obvious rather than habitual. The second half walks the LINQ operators worth memorising: Where, Select, SelectMany, GroupBy, OrderBy, Any, All, First versus FirstOrDefault, ToLookup, and the aggregate family.

Each lesson pairs a one-screen summary with a runnable snippet, and the downloadable cheat sheet mirrors the same layout so you can keep it open while you work. It is deliberately short: no project, no detours, just the decisions you make several times a day.

Topics covered

Frequently asked questions

Still unsure about something? Write to misteryjj100@gmail.com and a human answers, usually the same working day.

Yes, a printable PDF and a Markdown version are part of the downloadable resources, both organised in the same order as the lessons.

No, this course is about in-memory collections. Query translation and EF Core behaviour, including the SQL that gets generated, are covered in the C# intermediate course.

The collection types come from the shared base class library, so the guidance transfers directly. F# also has its own immutable list, map and set, which the final lesson compares briefly.

Checkout is handled on our provider's secure payment page. The moment your payment clears we email your personal access link and access code to the address you used at checkout, and the same link appears in your account library. There is nothing to install and nothing to wait for.

Email misteryjj100@gmail.com within 14 days of your purchase, quote your order number, and we refund the full amount to your original payment method. No form to fill in and no questions about how much of the course you watched.

What students say

Reviews are written by people who bought this course. We publish the critical ones too.

4.2

Rated 4.2 out of 5

Course rating · 5 reviews

Rating distribution

  • 5 stars 40%
  • 4 stars 40%
  • 3 stars 20%
  • 2 stars 0%
  • 1 star 0%
  • WA

    Wiktor Adamczyk

    Backend engineer

    Feb 2026
    Rated 5.0 out of 5

    The decision tree is pinned above my desk

    That one flowchart for choosing a collection is the most useful page of C# reference I own. Dictionary against HashSet against a sorted structure, settled in ten seconds instead of another browser tab.
  • AY

    Aiko Yamamoto

    .NET developer

    Nov 2025
    Rated 5.0 out of 5

    Frozen collections were a blind spot

    I have been writing C# since the framework days and had never touched FrozenDictionary. The benchmark showing where the up-front build cost stops being worth it is exactly the kind of detail that makes a short course like this pay for itself.
  • SD

    Sean Doherty

    Aug 2025
    Rated 4.0 out of 5

    Does what it says on the tin

    Under an hour, printable summary at the end, no waffle in between. The operator coverage plays it safe and stops around GroupBy and SelectMany, though it is upfront about being the ones worth memorising rather than the full set.
  • IR

    Isabel Rodríguez

    Software engineer

    May 2025
    Rated 4.0 out of 5

    The immutable chapter drags

    Handy overall, but a long stretch is spent selling me on why immutability is desirable when I had already bought in and wanted the trade-offs table. Everything either side of that is tight.
  • LN

    Lars Nyberg

    Tech lead

    Nov 2024
    Rated 3.0 out of 5

    The sheet is better than the videos

    Honestly the printable summary is worth the three pounds and the video is optional. Watching someone read a comparison table aloud is not a good use of forty minutes, and there is almost no worked example where picking the wrong collection produces a slowdown you can actually see. Buy it for the sheet and skip ahead.

Your instructor

YT

Yuki Tanaka

Game developer and C# instructor

  • 120 students taught
  • 5 courses published
  • 4.3 instructor rating
  • C#
  • .NET
  • Unity
  • Gameplay programming

Yuki has shipped six commercial titles, four of them solo, across PC and mobile. She teaches C# and .NET the way small studios actually use them — inside Unity, under a deadline — so the language lessons and the engine lessons arrive together. Students finish a playable game in every course, complete with menus, save files and a distributable build. She mentors at game jams most weekends and has judged three of them.

See every course by Yuki Tanaka
$3 USD

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