What Is .NET Core?
.NET Core is Microsoft's open-source, cross-platform runtime and set of libraries for building applications that run on Windows, Linux, and macOS. Unlike the original .NET Framework, which was tied to Windows, .NET Core was designed from the ground up to be modular, fast, and deployable in containers or on cloud infrastructure without a Windows dependency.
Cricket analogy: Just as a bilateral cricket series can now be played on neutral venues in the UAE instead of only the home team's stadium, .NET Core runs the same application logic on Windows, Linux, or macOS instead of being locked to one 'home ground'.
From .NET Framework to .NET Core
.NET Framework, released in 2002, was a Windows-only platform tightly coupled to the operating system and shipped as a single monolithic installation. .NET Core, first released in 2016, split the runtime into the CoreCLR execution engine and a set of NuGet-distributed libraries, allowing applications to carry their own runtime version and avoid the 'it works on my machine' problem caused by shared, machine-wide framework versions.
Cricket analogy: Just as cricket evolved from only Test matches to also include the self-contained, faster T20 format that doesn't need five days of shared 'infrastructure', .NET Core is a leaner, self-contained evolution of the older, heavier .NET Framework.
Cross-Platform and Open Source
The full .NET Core source code is hosted on GitHub under the MIT license, and Microsoft accepts community contributions to the runtime, the base class libraries, and the compiler (Roslyn). This openness means the JIT compiler, garbage collector, and libraries are inspectable and extensible by third parties, which has driven adoption by companies like Unity, Samsung, and Stack Overflow for production workloads.
Cricket analogy: Like how the DRS (Decision Review System) technology used in international cricket has publicly documented rules that any board can scrutinize, the .NET Core runtime's internals are open on GitHub for anyone to inspect.
The Unified .NET (5+)
Starting with .NET 5 in November 2020, Microsoft merged .NET Core, .NET Framework, Mono (used for Xamarin and Unity), and Xamarin into a single product line simply called '.NET', dropping the word 'Core' from branding while keeping the yearly release cadence (.NET 6, 7, 8, 9...). Even-numbered versions like .NET 6, 8, and 10 are Long-Term Support (LTS) releases supported for three years, while odd-numbered versions are Standard-Term Support (STS) supported for 18 months.
Cricket analogy: Like the ICC unifying separate domestic T20 leagues under one global calendar (the Future Tours Programme), Microsoft unified .NET Core, .NET Framework, and Xamarin/Mono into one release train starting with .NET 5.
# Check installed .NET SDKs and runtimes
dotnet --list-sdks
dotnet --list-runtimes
# Create and run a minimal .NET 8 console app
dotnet new console -n HelloCore
cd HelloCore
dotnet run
Since .NET 5, 'Core' is no longer part of the official product name — Microsoft calls it simply '.NET'. The term '.NET Core' is still commonly used informally (and in this course) to refer to the modern, cross-platform .NET line as opposed to the legacy Windows-only .NET Framework.
- .NET Core is Microsoft's open-source, cross-platform successor to the Windows-only .NET Framework.
- It splits the runtime (CoreCLR) from the libraries, allowing apps to carry their own pinned runtime version.
- The full source is on GitHub under the MIT license, accepting external contributions.
- Starting with .NET 5 (Nov 2020), .NET Core, .NET Framework, and Mono/Xamarin were unified into one '.NET' product line.
- Even-numbered versions (.NET 6, 8, 10) are LTS releases supported for 3 years; odd versions are STS, supported for 18 months.
- .NET Framework remains supported for legacy Windows apps but receives no new feature investment.
- Cross-platform support means the same app can run unmodified on Windows, Linux, and macOS.
Practice what you learned
1. What license is the .NET Core source code released under?
2. Starting with which version did Microsoft unify .NET Core, .NET Framework, and Mono/Xamarin into a single '.NET' product line?
3. Which of these is a key architectural difference between .NET Core and the original .NET Framework?
4. What support duration do even-numbered .NET releases (e.g., .NET 8) typically receive?
5. Which command lists the .NET SDKs installed on a machine?
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