Microsoft .NET Framework

Description

Microsoft developed .NET Framework as a free software platform that Windows applications use to run. Most users don’t encounter it as a program that they chose to install, but as a requirement that pops up when installing something else — a game, a business tool, a utility app — with a message saying the software needs .NET Framework before it can run. In those cases, Windows either has the right version installed, or it prompts the user to download it from Microsoft.

For developers, .NET Framework is the foundation on which they develop Windows applications. It offers the tools, programming languages, and libraries that make writing Windows software faster and more reliable than writing everything from scratch.

FOR USERS: WHAT IT DOES and WHY IT MATters

When a program requires .NET Framework, it means that program was built using Microsoft’s development tools and relies on .NET Framework to run properly on the computer. The framework serves as a layer between the application and Windows itself, performing tasks that every program requires — loading files, managing memory, drawing the user interface on screen and connecting to the internet or a database.

Most Windows computers already have one or more versions of .NET Framework installed. Windows Vista and later versions come with at least one version built in. When a program requests a particular version that is not currently on the computer, Windows Update can usually install it automatically, or the user downloads the installer directly from Microsoft at no cost.

Multiple versions of .NET Framework can coexist on the same computer at the same time without conflict. A program designed for version 3.5 runs on the version 3.5 runtime even if version 4.8 is also installed. Users never have to uninstall an older version to make room for a newer one.

FOR DEVELOPERS: HOW IT WORKS

.NET Framework has two major components: the Common Language Runtime (CLR) and the Framework Class Library (FCL).

The CLR is the engine that actually executes .NET applications. When a developer writes code in C#, F#, or Visual Basic and compiles it, the compiler does not generate machine code that can be run directly by the processor. Instead, it generates an intermediate format known as Common Intermediate Language (CIL). The CLR then takes that CIL code and converts it into native machine instructions at run-time using a process called Just-In-Time (JIT) compilation. This translation occurs on the fly as each part of the program is executed for the first time. The CLR also manages memory management automatically through garbage collection, which tracks objects the program no longer uses and frees that memory without the developer having to do it manually.

The Framework Class Library provides developers with a large library of code that they can call from their own programs. Rather than writing code to handle common tasks — reading and writing files, sending network requests, encrypting data, drawing windows and buttons on screen, querying a database — developers call functions that Microsoft already wrote and tested. This library covers thousands of common tasks and covers web applications through ASP.NET, desktop applications through Windows Forms and Windows Presentation Foundation (WPF), data access through ADO.NET, and service-oriented architecture through Windows Communication Foundation (WCF).

Language interoperability is another important feature. Because all .NET languages compile down to the same CIL intermediate format, a library written in Visual Basic works seamlessly in a C# project. Developers choose the language they like and still benefit from every library written in any other .NET language.

SUPPORTED LANGUAGES

.NET Framework supports application development in C#, Visual Basic, and F#. Third parties also developed compilers targeting .NET for other languages over the years. C# is the most popular language used for .NET development today and has a syntax inspired by C and Java.

VERSION HISTORY

Microsoft first released .NET Framework 1.0 in February 2002. Over the next 20 years, Microsoft released versions 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.6, 4.7 and finally 4.8 in April 2019. Version 4.8.1, released in August 2022, is the last version that Microsoft plans to release. Going forward, Microsoft focuses new development on the modern .NET platform (versions 5 and later), running on Windows, macOS, and Linux.NET Framework itself is still supported and continues to ship with Windows, but only gets security and reliability fixes, not new features.

Earlier versions such as 4.5.2, 4.6 and 4.6.1 reached end of support on April 26, 2022. Version 3.5 Service Pack 1 continues to receive support as a standalone product. Microsoft has said it has no plans to remove .NET Framework from Windows.

THE SHIFT TO MODERN .NET

Starting with .NET 5 in 2020, Microsoft merged .NET Framework and its cross-platform successor .NET Core into a single platform called .NET. The modern .NET platform (currently at version 9) runs on Windows, MacOS, and Linux, supports cloud and mobile development in addition to desktop and web, and gets a new major version every year. Microsoft recommends .NET for all new development. Existing applications built on .NET Framework continue to run without changes, and Microsoft supports migrating them to modern .NET for teams that want access to newer features and cross-platform capability.

SYSTEM Requirements and Installation

.NET Framework is a Windows-based framework. Different versions of .NET Framework have different minimum Windows versions. Version 4.8, the most current major release, requires Windows 7 Service Pack 1 or later. Version 3.5, which is often needed by older software, runs on Windows XP Service Pack 2 through current Windows 11. On Windows 8 and later, version 3.5 is an optional Windows feature that users enable via Control Panel instead of downloading a separate installer.