Object-Oriented Programming (OOP) and Patterns

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

Object-Oriented Programming and Patterns

C# is an object-oriented language. This section explores concepts such as classes, inheritance, and polymorphism, along with SOLID principles. Commonly used design patterns like Factory, Singleton, and Observer are also covered.

Goal: Increase code reusability and build maintainable systems.

TL;DR

Class, Property, Method → OOP fundamentals.
Interfaces and abstract classes.
SOLID + design patterns.

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.

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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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In C#, use Any() instead of checking Count > 0 to see if a collection contains items. This is more readable and often more efficient.


// Less readable
if (items.Count > 0)
{
    Console.WriteLine("Items exist");
}

// Recommended
if (items.Any())
{
    Console.WriteLine("Items exist");
}

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#, 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

When comparing strings in C#, using StringComparison helps prevent culture- and case-related bugs.


string a = "london";
string b = "LONDON";

bool eq1 = a == b;
bool eq2 = string.Equals(a, b, StringComparison.OrdinalIgnoreCase);

Console.WriteLine(eq1); // False
Console.WriteLine(eq2); // True

In C#, the null-coalescing operator (??) allows you to provide a default value when a variable is null.


string? userName = null;

// Old approach
string name1 = userName != null ? userName : "Guest";

// Recommended approach
string name2 = userName ?? "Guest";

Console.WriteLine(name1); // Guest
Console.WriteLine(name2); // Guest