Introduction to C#
Last Updated :
08 Oct, 2025
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C# (C-sharp) is a modern, object-oriented language created by Microsoft in 2000 as part of the .NET framework. It is used to build Windows applications, web services and more. C# combines the power of C/C++ with the simplicity of Java and Visual Basic.
Why use C#?
- Easy to learn: Clear, readable syntax, familiar to Java/C++ developers.
- Object-Oriented: Supports OOP principles (encapsulation, inheritance, polymorphism).
- Cross-platform: Build desktop, web, mobile, cloud and game applications.
- Rich libraries & frameworks: Large .NET library for faster development.
- Memory management: Automatic garbage collection reduces memory leaks.
- Modern features: LINQ, async/await and other powerful tools.
Applications of C#
- Windows Applications: Used to build desktop apps with frameworks like WPF and WinForms.
- Web Applications & Services: Powers dynamic websites, APIs and services using ASP.NET / ASP.NET Core.
- Game Development: Popular in Unity engine, one of the most widely used game development platforms.
- Mobile Applications: Supports cross-platform apps with Xamarin and .NET MAUI.
- Cloud & Enterprise Solutions: Widely used for scalable applications on Microsoft Azure and enterprise software.
Basic Program in C#
using System;
namespace HelloGeeksApp{
class HelloGeeks{
static void Main(string[] args){
Console.WriteLine("Hello Geek!");
Console.ReadKey();
}
}
}
Output
Hello Geek!
Explanation
- Program starts execution from the Main method.
- Console.WriteLine("Hello Geek!"): prints "Hello Geek!" on the console.
- Console.ReadKey(): waits for the user to press a key so the console window doesn’t close immediately.
Keywords
- using: lets you use classes from a namespace without full names.
- System: built-in namespace that has basic classes (like Console).
- namespace: groups related classes together (like a folder).
- class: defines a class (container for code).
- HelloGeeks: name of your class.
- static: method belongs to the class itself, no object needed.
- void: return type meaning “no value returned”.
- string[] args: stores command-line arguments (optional input).
Frameworks and Technologies
C# works closely with the .NET ecosystem, which provides the runtime, libraries and tools for application development. Over time, several frameworks and technologies have evolved around C# to support diverse platforms.
1. .NET Framework
- The original Windows-only platform for building desktop and web applications.
- Commonly used for WPF, WinForms and ASP.NET applications.
2. .NET Core
- Cross-platform, open-source version of .NET.
- Used to build apps that run on Windows, Linux and macOS.
- Supports web APIs, microservices and command-line tools.
3. .NET 5 and Later (.NET Unified Platform)
- Unifies .NET Framework and .NET Core into a single platform.
- Provides performance improvements and cross-platform support for all application types.
4. ASP.NET and ASP.NET Core
- Frameworks for developing dynamic web applications, RESTful APIs and MVC-based web services.
5. Entity Framework Core (EF Core)
- Object-Relational Mapper (ORM) for database operations.
- Allows developers to interact with databases using C# objects instead of SQL queries.
6. Unity Engine
- A game development platform that uses C# scripts for game logic.
- Powers 2D, 3D, AR and VR games across platforms like PC, consoles and mobile.
Advantages of C#
- Automatic garbage collection: reduces memory leaks and makes memory management easy.
- Safe and low maintenance: reliable compared to many other languages.
- Cross-platform via IL: compiled into Intermediate Language, independent of OS/architecture.
- Easy to learn: clear syntax, familiar to Java/C++ programmers.
- Rich standard library: many built-in classes and features.
- Strongly typed: reduces errors and improves reliability.
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