Collections in C#

C# is a powerful programming language that provides developers with a rich set of built-in data structures known as collections. Collections in C# are used to store and manipulate groups of related data items. In this article, we’ll explore the basics of collections in C# and how they can be used in your applications.

What are Collections in C#?

Collections in C# are classes that provide a way to store and manipulate groups of related data items. There are several types of collections in C#, including arrays, lists, dictionaries, queues, and stacks. Each collection type has its own unique characteristics and can be used in different situations depending on your application’s requirements.

Arrays

An array is a collection of elements of the same data type, stored in contiguous memory locations. Arrays in C# are fixed in size, meaning that once an array is created, its size cannot be changed. To access an element of an array, you can use the index of the element, which starts at 0. For example, to create an array of integers, you can use the following code:

int[] numbers = new int[5];

Lists

A list is a dynamic collection of elements of the same data type. Unlike arrays, lists can grow or shrink in size dynamically as elements are added or removed. Lists in C# are implemented using the List<T> class. To create a list of integers, you can use the following code:

List<int> numbers = new List<int>();

Dictionaries

A dictionary is a collection of key-value pairs, where each key is unique and corresponds to a value. Dictionaries in C# are implemented using the Dictionary<TKey, TValue> class. To create a dictionary of strings, you can use the following code:

Dictionary<string, string> contacts = new Dictionary<string, string>();

Queues

A queue is a collection of elements that supports adding elements to the back of the queue and removing elements from the front of the queue. Queues in C# are implemented using the Queue<T> class. To create a queue of integers, you can use the following code:

Queue<int> numbers = new Queue<int>();

Stacks

A stack is a collection of elements that supports adding elements to the top of the stack and removing elements from the top of the stack. Stacks in C# are implemented using the Stack<T> class. To create a stack of strings, you can use the following code:

Stack<string> names = new Stack<string>();

LINQ and Collections in C#

LINQ, or Language-Integrated Query, is a powerful feature of C# that allows you to query and manipulate collections of data in a concise and easy-to-read way. LINQ queries are written using a syntax that is similar to SQL, making it easy for developers who are familiar with SQL to transition to using LINQ.

To use LINQ with collections in C#, you must first have a collection to work with. Once you have a collection, you can use LINQ to query and manipulate the data in the collection. For example, to filter a list of integers to only include even numbers, you can use the following LINQ query:

List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6 };
var evenNumbers = from n in numbers
                  where n % 2 == 0
                  select n;

This query uses the “from” and “where” keywords to specify which elements of the list to include in the result, and the “select” keyword to specify which data to include in the final result.

Generics and Collections in C#

Generics are a powerful feature of C# that allow you to create classes, structures, and methods that work with any data type. Generics are often used in conjunction with collections in C# to create type-safe collections that can work with any data type.

For example, the List<T> class is a generic class that allows you to create a list of elements of any data type. To create a list of integers, you can use the following code:

List<int> numbers = new List<int>();

This code creates a new list of integers using the List<T> class. Because the List<T> class is generic, it can work with any data type, not just integers.

In addition to the List<T> class, there are many other generic collection classes in C#, including dictionaries, queues, and stacks. By using generics, you can create type-safe collections that are easy to use and maintain.

Conclusion

Collections in C# are an essential part of the language and provide developers with a powerful way to store and manipulate groups of related data items. Whether you need to store a fixed-size array, a dynamic list, a dictionary of key-value pairs, a queue, or a stack, C# has a collection type that can meet your needs. By understanding the basics of collections in C#, you can take advantage of these powerful tools to build better and more efficient applications