Language Service Essentials

To integrate a programming language into Visual Studio, you must provide a language service. You can develop the service in either managed or native code.

• For native code, you can use the Babel package. The Visual Studio Language Package project creates most of the components you need. For more information, see Implementing a Native-Code Language Service By Using Babel.

• For managed code, you can use the Managed Package Framework. For more information, see Implementing a Language Service By Using the Managed Package Framework.

• For managed code, you can use Managed Babel components. For more information, see Managed Babel.

• For either managed or native code, you can implement the language service interfaces directly. For more information, see Checklist: Creating a Language Service.

Visual Studio uses language services to provide the following features:

Feature	Description
Syntax coloring	Causes the editor view to display different colors and font styles for the different elements of a language. This differentiation can make it easier to read and edit files. For general information, see Syntax Coloring. For information about this feature in the managed package framework (MPF), see Syntax Colorizing (Managed Package Framework).
Statement completion	Completes a statement or keyword that the user has started typing. Statement completion helps users enter difficult statements more easily, with less typing and fewer chances for error. For general information, see Statement Completion. For information about this feature in the MPF, see IntelliSense Complete Word (Managed Package Framework).
Brace matching	Highlights paired characters such as braces. When the user types a closing character such as "}", brace matching highlights the corresponding opening character, such as "{". When there are several levels of enclosing characters, this feature helps users confirm that the enclosing characters are paired correctly. For information about this feature in the MPF, see Brace Matching (Managed Package Framework).
Parameter information tooltips	Displays a list of possible signatures for the overloaded method that the user is currently typing. For general information, see Parameter Info Tooltips. For information about this feature in the MPF, see IntelliSense Parameter Info (Managed Package Framework).
Error markers	Displays a wavy red underline, also known as a squiggly, under text that is syntactically incorrect. Error markers usually are used to make users aware of misspelled keywords, unclosed parentheses, invalid characters, and similar errors. For general information, see How to: Implement Error Markers. In the MPF classes, error markers are handled automatically in the AddError method of the AuthoringSink class.

Many of these features require the language service to parse source code. You often can reuse the tokenizing and parsing code for your compiler or interpreter.

The following features are related to support for programming languages but are not part of language services:

Feature	Description
Expression evaluators	Supports the Visual Studio debugger by validating breakpoints and supplying a list of expressions to be displayed in the Autos debug window. For more information, see Language Service Support for Debugging.
Symbol-browsing tools	Supports Object Browser, Class View, Call Browser, and Find Symbol Results.