Get started with language service and editor extensions
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
You can use editor extensions to add language service features such as outlining, brace matching, IntelliSense, and light bulbs to your own programming language or to any content type. You can also customize the appearance and behavior of the Visual Studio editor, for example text coloring, margins, adornments, and other visual elements. You can also define your own type of content, and specify the appearance and behavior of the text views in which your content appears.
To get started writing editor extensions, use the editor project templates that are installed as part of the Visual Studio SDK. The Visual Studio SDK is a downloadable set of tools that make it easier to develop Visual Studio extensions, either by using VSPackages or by using the Managed Extensibility Framework (MEF).
Note
For more information about the Visual Studio SDK, see Visual Studio SDK.
We recommend that you learn about the following concepts and technologies before you write your own editor extensions.
The Windows Presentation Foundation (WPF) and editor extensions
The Visual Studio editor user interface (UI) is implemented by using the Windows Presentation Foundation (WPF). The WPF provides a rich visual experience and a consistent programming model that separates the visual aspects of the code from the business logic. You can use many WPF elements and features when you create editor extensions. For more information, see Windows Presentation Foundation.
The Managed Extensibility Framework (MEF) and editor extensions
The Visual Studio editor uses the Managed Extensibility Framework (MEF) to manage its components and extensions. The MEF also lets developers more easily create extensions for a host application like Visual Studio. In this framework, you define an extension according to a MEF contract and export it as a MEF component part. The host application manages the component parts by finding them, registering them, and making sure that they are applied to the correct context.
Note
For more information about the MEF in the editor, see Managed Extensibility Framework in the editor.
Visual Studio editor extension points and extensions
Editor extension points are MEF component parts that you can customize and extend. In some cases you extend the extension point by implementing an interface and exporting it together with the correct metadata. In other cases you just declare an extension and export it as a particular type.
The following are some of the basic kinds of editor extensions:
Margins and scrollbars
Tags
Adornments
Options
IntelliSense
For more information about editor extension points, see Language service and editor extension points.
Deploying editor extensions
In Visual Studio, you deploy editor extensions by adding a metadata file named source.extension.vsixmanifest to the solution, building the solution, and then adding a copy of the binary files and the manifest in a folder that is known to Visual Studio. The manifest file defines the basic facts about the extension (for example, name, author, version, and type of content). For more information about the VSIX manifest file and how to deploy extensions, see Ship Visual Studio extensions.
When you install an extension on a computer, include the binaries and the manifest in a subfolder of folder that is known to Visual Studio.
Warning
You do not have to worry about the details of manifests and deployment locations if you use one of the editor extensibility templates that are included in Visual Studio. The templates contain everything that is required to register and deploy an extension.
Run extensions in the experimental instance
You can insulate your working version of Visual Studio while you are developing an extension by deploying it in the following experimental folder (on Windows Vista and Windows 7):
{%LOCALAPPDATA%}\VisualStudio\10.0Exp\Extensions\{Company}\{ExtensionID}
where %LOCALAPPDATA% is the name of the logged-on user, Company is the name of the company that owns the extension, and ExtensionID is the ID of the extension.
When you deploy an extension to the experimental location, it runs in debug mode. A second instance of Visual Studio is started, and is named Microsoft Visual Studio - Experimental Instance.
Manage extensions
Extensions to Visual Studio are listed in Extensions and Updates (on the Tools menu). If you are testing an extension in the experimental instance, it is listed in Extensions and Updates in the experimental instance, but is not listed in the development instance.
For more information, see Find and use Visual Studio extensions.
Use templates to create editor extensions
You can use editor templates to create MEF extensions that customize classifiers, adornments, and margins. There are templates for both C# and Visual Basic projects. For more information, see Create an extension with an editor item template.
You can also use the VSIX Project template to create extensions. This template provides only the elements that are required to deploy any kind of extension, and include the source.extension.vsixmanifest file, the required assembly references, and a project file that includes the build tasks that allow you to deploy the extension. For more information, see VSIX project template.
You can also create editor MEF components from a Visual Studio Package extension. See the following walkthroughs for details: