【.NET Framework & C#】Get started with the .NET Framework

Get started with the .NET Framework

The .NET Framework is a runtime execution environment that manages apps that target the .NET Framework. It consists of the common language runtime, which provides memory management and other system services, and an extensive(adj. 广泛的；大量的；广阔的) class library, which enables programmers to take advantage of robust(adj. 强健的；健康的；粗野的；粗鲁的), reliable code for all major areas of app development.

Note

The .NET Framework is available on Windows systems only. You can use .NET Core to run apps on Windows, MacOS, and Linux.

What is the .NET Framework?

The .NET Framework is a managed execution environment for Windows that provides a variety of services to its running apps. It consists of two major components: the common language runtime (CLR), which is the execution engine(n. 引擎，发动机；机车，火车头；工具) that handles running apps, and the .NET Framework Class Library, which provides a library of tested, reusable(adj. 可以再度使用的，可重复使用的) code that developers can call from their own apps. The services that the .NET Framework provides to running apps include the following:

• Memory management. In many programming languages, programmers are responsible for allocating and releasing memory and for handling object lifetimes. In .NET Framework apps, the CLR provides these services on behalf of the app.

• A common type system. In traditional programming languages, basic types are defined by the compiler(n. 编译器；[计] 编译程序；编辑者，汇编者), which complicates cross-language interoperability(n. [计] 互操作性；互用性). In the .NET Framework, basic types are defined by the .NET Framework type system and are common to all languages that target the .NET Framework.

• An extensive class library. Instead of having to write vast amounts of code to handle common low-level programming operations, programmers use a readily accessible library of types and their members from the .NET Framework Class Library.

• Development frameworks and technologies. The .NET Framework includes libraries for specific areas of app development, such as ASP.NET for web apps, ADO.NET for data access, Windows Communication Foundation for service-oriented apps, and Windows Presentation Foundation for Windows desktop apps.

• Language interoperability. Language compilers that target the .NET Framework emit an intermediate(vi. 起媒介作用 adj. 中间的，中级的) code named Common Intermediate Language (CIL), which, in turn, is compiled at runtime by the common language runtime. With this feature, routines(n. 常规，惯例) written in one language are accessible to other languages, and programmers focus on creating apps in their preferred languages.

• Version compatibility. With rare exceptions, apps that are developed by using a particular version of the .NET Framework run without modification on a later version.

• Side-by-side execution. The .NET Framework helps resolve version conflicts by allowing multiple versions of the common language runtime to exist on the same computer. This means that multiple versions of apps can coexist(vi. 共存；和平共处) and that an app can run on the version of the .NET Framework with which it was built. Side-by-side execution applies to the .NET Framework version groups 1.0/1.1, 2.0/3.0/3.5, and 4/4.5.x/4.6.x/4.7.x.

• Multitargeting. By targeting .NET Standard, developers create class libraries that work on multiple .NET Framework platforms supported by that version of the standard. For example, libraries that target the .NET Standard 2.0 can be used by apps that target the .NET Framework 4.6.1, .NET Core 2.0, and UWP 10.0.16299.

The .NET Framework for users

If you don't develop .NET Framework apps, but you use them, you aren't required to have specific knowledge about the .NET Framework or its operation. For the most part, the .NET Framework is completely transparent to users.

If you're using the Windows operating system, the .NET Framework may already be installed on your computer. In addition, if you install an app that requires the .NET Framework, the app's setup program might install a specific version of the .NET Framework on your computer. In some cases, you may see a dialog box that asks you to install the .NET Framework. If you've just tried to run an app when this dialog box appears and if your computer has Internet access, you can go to a webpage that lets you install the missing version of the .NET Framework. For more information, see the Installation guide.

In general, you shouldn't uninstall versions of the .NET Framework that are installed on your computer. There are two reasons for this:

• If an app that you use depends on a specific version of the .NET Framework, that app may break if that version is removed.

• Some versions of the .NET Framework are in-place updates to earlier versions. For example, the .NET Framework 3.5 is an in-place update to version 2.0, and the .NET Framework 4.7.2 is an in-place update to versions 4 through 4.7.1. For more information, see .NET Framework Versions and Dependencies.

On Windows versions before Windows 8, if you do choose to remove the .NET Framework, always use Programs and Features from Control Panel to uninstall it. Never remove a version of the .NET Framework manually. On Windows 8 and above, the .NET Framework is an operating system component and cannot be independently uninstalled.

The .NET Framework for developers

If you're a developer, choose any programming language that supports the .NET Framework to create your apps. Because the .NET Framework provides language independence and interoperability, you interact with other .NET Framework apps and components regardless of the language with which they were developed.

To develop .NET Framework apps or components, do the following:

1. If it's not preinstalled on your operating system, install the version of the .NET Framework that your app will target. The most recent production version is the .NET Framework 4.7.2, which is preinstalled on Windows 10 April 2018 Update and is available for download on earlier versions of the Windows operating system. For .NET Framework system requirements, see System Requirements. For information on installing other versions of the .NET Framework, see Installation Guide. Additional .NET Framework packages are released out of band, which means that they're released on a rolling basis outside of any regular or scheduled release cycle. For information about these packages, see The .NET Framework and Out-of-Band Releases.

2. Select the language or languages supported by the .NET Framework that you intend to use to develop your apps. A number of languages are available, including Visual Basic, C#, F#, and C++/CLI from Microsoft. (A programming language that allows you to develop apps for the .NET Framework adheres to the Common Language Infrastructure (CLI) specification.)

3. Select and install the development environment to use to create your apps and that supports your selected programming language or languages. The Microsoft integrated development environment (IDE) for .NET Framework apps is Visual Studio. It's available in a number of editions.

For more information on developing apps that target the .NET Framework, see the Development Guide.

Related topics

Title	Description
Overview	Provides detailed information for developers who build apps that target the .NET Framework.
Installation guide	Provides information about installing the .NET Framework.
The .NET Framework and Out-of-Band Releases	Describes the .NET Framework out of band releases and how to use them in your app.
System Requirements	Lists the hardware and software requirements for running the .NET Framework.
.NET Core and Open-Source	Describes .NET Core in relation to the .NET Framework and how to access the open-source .NET Core projects.
.NET Core documentation	Provides the conceptual and API reference documentation for .NET Core.
.NET Standard	Discusses .NET Standard, a versioned specification that individual .NET implementations support to guarantee that a consistent set of APIs are available on multiple platforms.

See also

.NET Framework Guide
What's New
.NET API Browser
Development Guide