# Collections in C#

Arrays have a fixed size; collections grow and shrink as you need. You will work with List&lt;T> and Dictionary<TKey, TValue>, the two collections you will use most.

Updated: November 3, 2026

## [Array Review in C#](https://www.ask-codey.com/courses/csharp-full-stack-bootcamp/topics/array-review-in-csharp)

1. [What Arrays Solve](https://www.ask-codey.com/lessons/array-review-in-csharp-what-arrays-solve) (Apprentice): A quick review of what arrays do well, fast access by position, one name for a group, and easy looping, before meeting their limits.
2. [But Arrays Can Be Tedious](https://www.ask-codey.com/lessons/array-review-in-csharp-but-arrays-can-be-tedious) (Apprentice): Arrays can't grow or shrink, so adding, inserting and removing elements means making new arrays and shifting values by hand.

## [Lists in C#](https://www.ask-codey.com/courses/csharp-full-stack-bootcamp/topics/lists-in-csharp)

1. [Introduction to List&lt;T>](https://www.ask-codey.com/lessons/lists-in-csharp-introduction-to-list-t) (Apprentice): A List&lt;T> holds values of one type and grows and shrinks for you; the T says which type, like int or string.
2. [Working with List&lt;T>](https://www.ask-codey.com/lessons/lists-in-csharp-working-with-list-t) (Apprentice): Add, insert, read, find, remove, sort and loop through the items of a C# List&lt;T>.

## [Dictionaries in C#](https://www.ask-codey.com/courses/csharp-full-stack-bootcamp/topics/dictionaries-in-csharp)

1. [Dictionaries in C#](https://www.ask-codey.com/lessons/dictionaries-in-csharp) (Apprentice): A Dictionary&lt;TKey, TValue> stores values under unique keys, so you can look one up by its label instead of its position.

## [Exercise: Collections](https://www.ask-codey.com/courses/csharp-full-stack-bootcamp/topics/exercise-collections)

1. [Exercise: Collections](https://www.ask-codey.com/lessons/exercise-collections) (Apprentice): Solve 14 problems with List&lt;T> and Dictionary&lt;TKey, TValue> (filtering, searching, counting, looking up and combining) and check each one with tests.

Source: https://www.ask-codey.com/courses/csharp-full-stack-bootcamp/chapters/collections-in-csharp