[C# Tutorial] C# Collection (Collection)

C# Collection

The Collection class is a class specially used for data storage and retrieval. These classes provide support for stacks, queues, lists, and hash tables. Most collection classes implement the same interface.

Collection classes serve different purposes, such as dynamically allocating memory for elements, accessing list items based on indexes, etc. These classes create collections of objects of the Object class. In C#, the Object class is the base class for all data types.

Various collection classes and their usage

The following are various commonly used classes in the System.Collection namespace. Click the link below for details.

Class

Description and Usage

Dynamic Array (ArrayList) It represents an ordered collection of objects that can be individually indexed.

It basically replaces an array. However, unlike arrays, where you can add and remove items at specified locations using indexes, a dynamic array automatically resizes it. It also allows dynamic memory allocation, addition, searching, and sorting of items in lists.

Hashtable (Hashtable) It uses keys to access elements in a collection.

When you access an element using a key, a hash table is used and you can identify a useful key value. Each item in the hash table has a key/value pair. Keys are used to access items in the collection.

Sorted List (SortedList) It can use keys and indexes to access items in the list.

A sorted list is a combination of an array and a hash table. It contains a list of items that can be accessed using a key or index. If you access items using indexes, it's a dynamic array (ArrayList), if you access items using keys, it's a hashtable (Hashtable). Items in a collection are always sorted by key value.

Stack (Stack) It represents a last-in-first-out collection of objects.

Use a stack when you need last-in-first-out access to items. When you add an item to the list, it is called a push element, and when you remove an item from the list, it is called a pop element.

Queue (Queue) It represents a first-in, first-out collection of objects.

Use a queue when you need first-in-first-out access to items. When you add an item to the list, it's called enqueuing, and when you remove an item from the list, it's called dequeuing.

Point Array (BitArray) It represents a binary array represented by the values ​​1 and 0.

When you need to store bits, but don't know the number of bits in advance, then use a point array. You can access items from a collection of point arrays using integer indexes, which start at zero.

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