🔹 .NET Framework vs .NET Core

 1. Introduction

• .NET Framework

  • Released in 2002 by Microsoft.

  • Runs only on Windows.

  • Used for building desktop apps (WinForms, WPF), ASP.NET Web Forms/MVC, enterprise solutions, etc.

  • Mature and widely used, but Windows-only and no active feature development (only security fixes now).

• .NET Core

  • Released in 2016 as a cross-platform, open-source re-implementation of .NET.

  • Runs on Windows, Linux, macOS.

  • Supports modern development (cloud, microservices, Docker, Kubernetes).

  • Actively developed and evolved into .NET 5+ (Unified .NET platform).

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2. Key Differences

Feature	.NET Framework	.NET Core
Platform Support	Windows-only	Cross-platform (Windows, Linux, macOS)
Deployment	Installed on Windows system	Self-contained (bundled with app) or framework-dependent
Performance	Good, but older runtime	High performance, optimized runtime (Kestrel web server)
Open Source	Mostly closed source	Fully open source (on GitHub)
Application Types	WinForms, WPF, ASP.NET Web Forms/MVC, WCF	ASP.NET Core (MVC, Razor Pages, Blazor), Console, Microservices
Cross-Platform Development	❌ No	✅ Yes
Microservices Support	Limited	Excellent (Docker + Kubernetes ready)
Cloud Support (Azure, AWS)	Supported but heavier	Optimized for cloud-native
Future	Maintenance only (no major new features)	Active development (merged into .NET 5, .NET 6, .NET 7, .NET 8, .NET 9 …)

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3. Architecture Differences

.NET Framework:

• Runs only with Windows OS + IIS (Internet Information Services) for hosting web apps.

• Traditional monolithic applications.

.NET Core:

• Uses Kestrel Web Server (lightweight, cross-platform).

• Can be hosted in IIS, Nginx, Apache, or Docker containers.

• Supports microservices architecture.

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4. Performance

• .NET Core apps are generally faster because of:

  • JIT (RyuJIT improvements)

  • Lightweight runtime

  • Optimized memory management

  • Kestrel (high-performance web server)

Example: ASP.NET Core can handle millions of requests/sec, while classic ASP.NET Framework is slower.

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5. Deployment

• .NET Framework: Installed on Windows; app depends on that system installation.

• .NET Core:

  • Framework-dependent deployment (FDD): App runs on shared runtime.

  • Self-contained deployment (SCD): App carries its own runtime — no need to install .NET separately.

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6. Ecosystem & Future

• .NET Framework → Legacy projects, Windows desktop apps (still relevant for enterprises).

• .NET Core → Foundation for modern apps.

• In 2020, Microsoft merged everything into a unified platform called .NET 5+ (now we are at .NET 9).

  • .NET Framework will never get new features.

  • .NET Core is the future path.

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7. When to Use

• ✅ Use .NET Framework if:

  • You are maintaining an existing Windows-only enterprise app.

  • You need technologies not yet available in .NET Core (like full WCF or Web Forms).

• ✅ Use .NET Core / .NET 5+ if:

  • You’re building new applications (web, microservices, cloud-native).

  • You want cross-platform support.

  • You care about performance and scalability.

  • You plan to use Docker, Kubernetes, or cloud hosting.

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🔑 Quick Summary

• .NET Framework = Old, Windows-only, legacy support.

• .NET Core = Modern, cross-platform, high-performance, future-ready (part of .NET 5+).