1. Introduction
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.NET Framework
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Released in 2002 by Microsoft.
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Runs only on Windows.
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Used for building desktop apps (WinForms, WPF), ASP.NET Web Forms/MVC, enterprise solutions, etc.
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Mature and widely used, but Windows-only and no active feature development (only security fixes now).
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.NET Core
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Released in 2016 as a cross-platform, open-source re-implementation of .NET.
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Runs on Windows, Linux, macOS.
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Supports modern development (cloud, microservices, Docker, Kubernetes).
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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 …) |
3. Architecture Differences
.NET Framework:
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Runs only with Windows OS + IIS (Internet Information Services) for hosting web apps.
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Traditional monolithic applications.
.NET Core:
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Uses Kestrel Web Server (lightweight, cross-platform).
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Can be hosted in IIS, Nginx, Apache, or Docker containers.
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Supports microservices architecture.
4. Performance
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.NET Core apps are generally faster because of:
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JIT (RyuJIT improvements)
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Lightweight runtime
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Optimized memory management
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Kestrel (high-performance web server)
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Example: ASP.NET Core can handle millions of requests/sec, while classic ASP.NET Framework is slower.
5. Deployment
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.NET Framework: Installed on Windows; app depends on that system installation.
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.NET Core:
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Framework-dependent deployment (FDD): App runs on shared runtime.
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Self-contained deployment (SCD): App carries its own runtime — no need to install .NET separately.
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6. Ecosystem & Future
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.NET Framework → Legacy projects, Windows desktop apps (still relevant for enterprises).
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.NET Core → Foundation for modern apps.
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In 2020, Microsoft merged everything into a unified platform called .NET 5+ (now we are at .NET 9).
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.NET Framework will never get new features.
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.NET Core is the future path.
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7. When to Use
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✅ Use .NET Framework if:
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You are maintaining an existing Windows-only enterprise app.
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You need technologies not yet available in .NET Core (like full WCF or Web Forms).
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✅ Use .NET Core / .NET 5+ if:
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You’re building new applications (web, microservices, cloud-native).
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You want cross-platform support.
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You care about performance and scalability.
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You plan to use Docker, Kubernetes, or cloud hosting.
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🔑 Quick Summary
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.NET Framework = Old, Windows-only, legacy support.
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.NET Core = Modern, cross-platform, high-performance, future-ready (part of .NET 5+).
