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Video Description
Real programs don't work with one variable at a time - they manage hundreds or thousands of items. Let's master collections in C#!
What you'll learn:
- Arrays - Fixed-size collections with indexed access
- Lists - Dynamic collections that grow as needed
- Dictionary - Lightning-fast key-value lookups
- HashSet - Automatic duplicate prevention
- How collections relate through interfaces (IEnumerable, IList)
- When to use each collection type
- Common gotchas (IndexOutOfRangeException, modifying during foreach)
- Performance characteristics (Big O notation simplified)
- Combining collections (Dictionary of Lists!)
Key insights:
- List is your default choice 90% of the time
- Arrays are rare in modern C# (fixed size is limiting)
- Dictionary lookups are O(1) - nearly instant!
- HashSet.Contains() beats List.Contains() for large data
- All collections implement IEnumerable (that's why LINQ works!)
We'll build:
- Grade tracker using multiple collection types
- Real examples with student data
- Collections inside collections
Next Video: LINQ - Query Your Data
Finally understanding when to use List vs Dictionary? Smash that like button! Subscribe and hit the bell - LINQ is next and it's going to change everything. What collection type confused you the most when starting out? Let me know below!
Chapters
- 0:00 Collections - Lists and Arrays
- 0:31 The Problem With Single Variables
- 1:10 Two really important namespaces:
- 1:35 Arrays - Your First Collection
- 2:19 Common Array Mistake
- 3:30 Lists - Dynamic Collections
- 4:19 Array vs List
- 5:31 Dictionary - Key-Value Pairs
- 6:24 HashSet - Unique Items Only
- 7:13 How Collections Fit Together
- 8:04 How Do I Choose?
- 8:14 Choosing the Right Collection
- 8:52 Real-World Example
- 9:33 Common Collection Gotchas
- 10:15 Performance Quick Reference
- 11:05 Key Takeaways
- 11:57 Practice Challenge
- 12:46 Next up: LINQ
Video Info
- Duration: 13:10
- Published: November 10, 2025
