Add Extensions to DSL Definitions
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
DSL Definition extension allows you to create a package of extensions to a domain-specific language (DSL). The DSL extension, which is contained in a Visual Studio Integration Extension (VSIX), can be installed on a user's computer in the same manner as a DSL. The additional features can be dynamically enabled and disabled at run time. DSLs do not have to be explicitly designed for extension, and extensions can be designed later, or by third parties, without altering the extended DSL.
DSL extensions can include the following features:
Properties for model and presentation elements
Decorators for shapes and connectors
Classes, relationships, shapes, and connectors
Validation constraints
Toolbox items and tabs
A user of an extended DSL can create and save a model that contains instances of the additional features. The model can be read by other users who have installed the appropriate extension. Users who have not installed the extension cannot use the additional features, but they can update and save a model without losing the additional features.
Note
The Text Template Transformation component is automatically installed as part of the Visual Studio extension development workload. You can also install it from the Individual components tab of Visual Studio Installer, under the SDKs, libraries, and frameworks category. Install the Modeling SDK component from the Individual components tab.