C# (.NET) Standard Library: Complete Overview

C# (.NET) Standard Library: Complete Overview

The C# (.NET) Standard Library is a fundamental set of namespaces, classes, interfaces, and methods that forms the foundation of the .NET platform. It provides the developer with ready-made solutions for most everyday tasks: from working with files and collections to multithreading and reflection. In this article, we will provide a complete overview of the key components of the C# (.NET) Standard Library with practical code examples.

1. System Namespace — The Foundation of Everything

The System namespace contains fundamental data types and base classes. This includes:

• Base types: Object, ValueType, String, Int32, Boolean, etc.
• Mathematical functions: the Math class (methods Abs, Pow, Sqrt).
• Working with the console: the Console class (input/output).
• Random number generation: the Random class.

using System;

class Program{    static void Main()    {        // Example of working with base types and the Math class        int number = -42;        int absoluteValue = Math.Abs(number);        Console.WriteLine($"The absolute value of {number} is {absoluteValue}");

        // Random number generation        Random rnd = new Random();        int randomNumber = rnd.Next(1, 100);        Console.WriteLine($"Random number from 1 to 100: {randomNumber}");    }}

2. System.Collections — Working with Collections

The System.Collections namespace and its generic version System.Collections.Generic provide classes for storing and managing groups of objects. The most popular ones are:

• List<T> — a dynamic array.
• Dictionary<TKey, TValue> — a key-value collection.
• Queue<T> — a queue (first in, first out).
• Stack<T> — a stack (last in, first out).
• HashSet<T> — a hash set of unique elements.

using System;using System.Collections.Generic;

class Program{    static void Main()    {        // List        List<string> fruits = new List<string> { "Apple", "Banana", "Orange" };        fruits.Add("Grape");        Console.WriteLine("List of fruits:");        foreach (var fruit in fruits)            Console.WriteLine(fruit);

        // Dictionary        Dictionary<int, string> employees = new Dictionary<int, string>();        employees.Add(1, "Ivan");        employees.Add(2, "Maria");        Console.WriteLine($"Employee with ID 1: {employees[1]}");    }}

3. System.Linq — Language Integrated Query (LINQ)

System.Linq is one of the most powerful extensions of the C# (.NET) Standard Library. It allows you to perform complex queries on collections, databases, and XML using syntax similar to SQL. Main extension methods:

• Where — filtering.
• Select — projection (transformation).
• OrderBy / OrderByDescending — sorting.
• GroupBy — grouping.
• Aggregate — aggregation (sum, maximum, etc.).

using System;using System.Collections.Generic;using System.Linq;

class Program{    static void Main()    {        List<int> numbers = new List<int> { 5, 12, 8, 21, 3, 17 };

        // Filtering and sorting using LINQ        var result = numbers.Where(n => n > 10)