C#

From language basics to LINQ, async/await, and the .NET ecosystem; modern features and best practices for production-ready apps.

What is C#?

C# is a statically typed language developed by Microsoft that blends object-oriented and functional features. With .NET 8 it is cross-platform (Windows, Linux, macOS) and used for web APIs, desktop apps, cloud services, background jobs, and games (Unity) across a wide range.

Ecosystem: ASP.NET Core (web), Entity Framework Core (data access), xUnit/NUnit (testing), NuGet (package management), and the dotnet CLI (command line).

TL;DR

Modern C#: records, pattern matching, async/await, and span/memory for performance.
Fast REST services with Minimal APIs; efficient CRUD and LINQ with EF Core.
Layered architecture + dependency injection for testable design.

Language Basics

Fundamentals of C# syntax, type system, and control flow. The first stop for beginners to grasp the logic of the language.

Introduction to C# and the .NET Ecosystem

11 January 2026 • Language Basics

C# is a modern, safe, and object-oriented language. With the .NET ecosystem, it is possible to develop web, mobile, desktop, and game applications.

C# C# Basics

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First C# Project

11 January 2026 • Language Basics

First console app in C# with Visual Studio 2022: usage of WriteLine, ReadKey, and ReadLine.

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C# Basic Data Types

11 January 2026 • Language Basics

Basic data types in C#: numeric, text, logical, object-based, and nullable types.

C# C# Basics Variables

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C# Syntax Structure

13 January 2026 • Language Basics

Learn the basics of C# syntax, including code blocks, comments, and variable naming rules, with clear explanations and practical examples.

C# Syntax

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C# Operators and Expressions

13 January 2026 • Language Basics

Operators and expressions in C#: arithmetic, comparison, logical, increment/decrement, ternary, and null-coalescing usage.

C# Operators

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C# Conditional Statements (if, else, switch)

13 January 2026 • Language Basics

Decision structures in C#: learn how to use if, else if, else and switch to perform different actions based on conditions.

C# else Statement if Statement switch Statement

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C# Loops (for, foreach, while, do-while)

17 January 2026 • Language Basics

Learn how to use for, foreach, while, and do-while loops in C#. Discover practical examples for handling repeated operations in C# applications.

C# do-while Loop for Loop foreach Loop while Loop

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C# Console Commands

17 January 2026 • Language Basics

Learn how to work with the C# console by writing output, reading user input, and formatting text with practical examples.

C# Console

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C# String Operations

17 January 2026 • Language Basics

Learn how to work with strings in C#, including concatenation, searching, substring, IndexOf, and other essential string operations.

C# String Operations

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C# Type Conversions

21 January 2026 • Language Basics

Learn how type conversions work in C#, including implicit and explicit casting, Parse, TryParse, and Convert methods with examples.

C# Type Conversion

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Using Constants and Enums in C#

21 January 2026 • Language Basics

Learn how to use constants and enums in C# to write cleaner, safer, and more maintainable code with clear explanations and examples.

C# Constants Enum

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C# Math Library

21 January 2026 • Language Basics

Learn how to use the C# Math library, including Pow, Sqrt, Round, Abs, and other essential mathematical methods with examples.

C# C# Math

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C# Boolean Operations

24 January 2026 • Language Basics

Learn how boolean operations work in C#, including the bool type, comparisons, and logical operators like &&, ||, and ! with examples.

Boolean C#

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DateTime & TimeSpan Operations in C#

24 January 2026 • Language Basics

Learn how to work with DateTime and TimeSpan in C# to perform date and time operations such as comparison, addition, subtraction, and formatting.

C# DateTime

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Random Operations in C#

27 January 2026 • Language Basics

Learn how to use the Random class in C# to generate random numbers, values, and selections using Next, NextDouble, and examples.

C# Random

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Methods and Parameter Usage in C#

27 January 2026 • Language Basics

Learn how to define methods and use parameters in C#, including value and reference parameters, optional parameters, and examples.

C# Methods Parameters

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C# Exception Handling (try, catch, finally)

30 January 2026 • Language Basics

Learn how to handle exceptions in C# using try, catch, and finally blocks to manage errors safely with clear examples.

C# Error Handling try-catch

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Namespaces and Assemblies in C#

30 January 2026 • Language Basics

Learn how namespaces and assemblies work in C# to organize code, manage dependencies, and structure projects effectively.

C# C# Namespace

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Object-Oriented Programming (OOP) and Patterns

Classes, inheritance, interfaces, and design patterns to write reusable and maintainable code in C#.

Class, Object, Property and Methods in C#

2 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn how classes, objects, properties, and methods work in C# and form the core building blocks of object-oriented programming.

C# C# Object-Oriented Programming Classes Methods

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Structs in C# – Differences from Classes

2 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn the key differences between structs and classes in C#, including memory model, inheritance, boxing, and performance.

C# C# Object-Oriented Programming Structs

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Constructors, Destructors and this in C#

2 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn how constructors, destructors, and the this keyword work in C# to manage object lifecycle and class-level access.

C# C# Object-Oriented Programming Classes

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Sealed, Static, and Partial Classes in C#

2 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn the purpose, differences, and use cases of sealed, static, and partial classes in C# with practical examples.

C# C# Object-Oriented Programming Classes

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Record Types and Immutable Objects in C#

5 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn C# record types and immutable objects, including value equality, with-expressions, and patterns for building safer data models.

C# C# Object-Oriented Programming Record Types

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Encapsulation, Inheritance, and Polymorphism in C#

5 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn encapsulation, inheritance, and polymorphism in C# with clear examples to understand core OOP principles and real use cases.

C# C# Object-Oriented Programming Classes Encapsulation Inheritance Polymorphism

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Interfaces and Abstract Classes in C#

5 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn interfaces and abstract classes in C#, their differences, and when to use each approach to design clean and extensible code.

C# C# Object-Oriented Programming Classes Interfaces

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Delegates and Events in C#

8 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn delegates and events in C# to build event-driven applications using callbacks, subscriptions, and real-world examples.

C# C# Delegates C# Events Object-Oriented Programming

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Lambda Expressions in C#

8 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn lambda expressions in C#, including concise syntax, Func and Action delegates, and practical LINQ usage examples.

C# LINQ

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Extension Methods in C#

8 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn extension methods in C# to add new functionality to existing types without modifying their source code.

C# Methods

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Dependency Injection Basics in C#

11 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn the basics of Dependency Injection in C#, including managing dependencies, loose coupling, and improving testability.

C# Dependency Injection

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SOLID Principles with C#

11 February 2026 • Object-Oriented Programming (OOP) and Patterns

Applying SOLID principles in C# with examples: building flexible, maintainable, and testable code.

C# SOLID Principles

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Design Patterns in C# (Factory, Singleton, Repository, Observer)

14 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn design patterns in C#, including Factory, Singleton, Repository, and Observer, to build flexible and maintainable applications.

C# Repository Pattern

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Interop in C# (Working with C/C++ Libraries)

14 February 2026 • Object-Oriented Programming (OOP) and Patterns

Learn how to use Interop in C# to work with C/C++ libraries, including P/Invoke, unmanaged code, and data marshaling.

C# C++ Interop

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Data and Collections

Arrays, collections, generics, and LINQ for effective data handling and querying in C#.

Arrays in C#

19 February 2026 • Data and Collections

Learn arrays in C#, including declaration, indexing, looping through elements, and common array operations with examples.

Arrays C#

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Collections in C#: List, Dictionary, Queue, Stack

19 February 2026 • Data and Collections

Learn C# collections like List, Dictionary, Queue, and Stack to store and manage data efficiently with practical examples.

C# C# Collections Dictionaries Lists Queues Stacks

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Generics in C# (List<T>, Dictionary<TKey,TValue>)

24 February 2026 • Data and Collections

Learn generics in C#, including List<T> and Dictionary<TKey,TValue>, to write type-safe and reusable code with examples.

C# C# Generics Dictionaries Lists

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LINQ Basics in C# (Where, Select, OrderBy)

26 February 2026 • Data and Collections

Learn LINQ basics in C# using Where, Select, and OrderBy to query, filter, and sort collections with practical examples.

C# LINQ Basics

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In C#, use class when objects are identified by who they are. Use record when objects are identified by their values.


// class: identity-based
class User
{
    public string Name { get; set; }
    public int Age { get; set; }
}

var u1 = new User { Name = "Alice", Age = 30 };
var u2 = new User { Name = "Alice", Age = 30 };

Console.WriteLine(u1 == u2); // False


// record: value-based
record UserRecord(string Name, int Age);

var r1 = new UserRecord("Alice", 30);
var r2 = new UserRecord("Alice", 30);

Console.WriteLine(r1 == r2); // True

In C#, FirstOrDefault() can return null. Always check the result before using it to avoid runtime errors.


// Risky usage
var user = users.FirstOrDefault();
Console.WriteLine(user.Name); // may throw an error

// Safe usage
var safeUser = users.FirstOrDefault();
if (safeUser != null)
{
    Console.WriteLine(safeUser.Name);
}

In C#, use is and is not for more readable type checks and pattern matching.


// Old approach (using "as" and null check)
object obj = "Hello, world!";
if (obj is string)
{
    Console.WriteLine(((string)obj).ToUpper()); // HELLO, WORLD!
}

// Recommended approach (using is)
if (obj is string str)
{
    Console.WriteLine(str.ToUpper()); // HELLO, WORLD!
}

// Using "is not" for negation
if (obj is not int)
{
    Console.WriteLine("Not an integer");
}

In C#, the ??= operator assigns a value only when the variable has no value (null). If the variable already has a value, it stays the same.


string? title = null;

// If title has no value, a value is assigned
title ??= "Untitled";
Console.WriteLine(title); // Untitled

// Since title already has a value, nothing changes
title ??= "New Title";
Console.WriteLine(title); // Untitled

In C#, nameof() returns the name of a variable, property, or method as text. This helps prevent errors caused by hard-coded strings.


int age = 25;

// Old approach
if (age < 0)
{
    throw new ArgumentException("age");
}

// Recommended approach
if (age < 0)
{
    throw new ArgumentException(nameof(age));
}

Console.WriteLine(nameof(age)); // age

In C#, use Guid.Empty instead of new Guid() when you want an empty GUID. It makes the code clearer.


// Less clear
Guid id1 = new Guid();

// Clear and recommended
Guid id2 = Guid.Empty;

Console.WriteLine(id1 == id2); // True

In C#, string interpolation ($"...") is more readable and safer than using String.Format.


int a = 18, b = 22;
string text;

// Old approach
text = string.Format("number1: {0}, number2: {1}", a, b);

// Recommended approach
text = $"number1: {a}, number2: {b}";

Using DateTime.UtcNow instead of DateTime.Now prevents timezone-related bugs in distributed systems.


// Local time (depends on server timezone)
DateTime localTime = DateTime.Now;

// Universal time (recommended)
DateTime utcTime = DateTime.UtcNow;

Console.WriteLine(localTime);
Console.WriteLine(utcTime);

In C#, use IEnumerable<T> when you only need to read and iterate over data. Use List<T> when you need to add, remove, or access items by index.


// Read-only usage: just iterate
IEnumerable<int> numbers = new[] { 10, 20, 30 };

foreach (var n in numbers)
{
    Console.WriteLine(n);
}

// List usage: modify or access by index
List<int> list = new List<int> { 10, 20, 30 };
list.Add(40);

Console.WriteLine(list[0]); // 10

In C#, const values are fixed at compile time, while readonly values can be assigned at runtime, usually in the constructor.


// const: value must be known at compile time
public const int MaxItems = 10;

// readonly: value can be set at runtime
public readonly int Timeout;

public Settings()
{
    Timeout = GetTimeoutFromConfig();
}