Visual Studio SDK and Automation
You can write Visual Studio applications by using automation, VSPackages, or a combination of the two. Automation add-ins can call Visual Studio services, and Visual Studio packages (VSPackages) can access the Visual Studio automation model. You can combine these two approaches to create an effective solution.
For an example of calling automation from a VSPackage, see Walkthrough: Extending Managed VSPackages By Using Automation. For an example of calling Visual Studio services from an automation add-in, see Walkthrough: Calling into the Visual Studio SDK By Using Automation.