Persistence and the Running Document Table
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
In the Visual Studio IDE, projects are completely responsible for managing the persistence of their project items, which they accomplish using the service, SVsRunningDocumentTable. Documents are the basic unit of persistence in the Visual Studio environment. Projects coordinate the opening, saving, and renaming of documents with the running document table (RDT), a resource that tracks the state of all open documents.
Managing Persistence
Projects control the environment's persistence service by implementing the IVsPersistHierarchyItem interface. While the environment never directly asks a document to persist itself, it asks the owning project (or hierarchy) to save the document. This makes it possible for the project to save its project item data into local files, remote files, a database, a repository, or other medium.
The global environment maintains the RDT. The environment maintains entries for all open windows and documents in the RDT, which makes it possible for them to receive special notifications, such as when a solution is closed. In addition, the RDT makes it possible for the environment to track their corresponding nodes in Solution Explorer. The RDT maintains one record per open, persistable object, including both project files and project-item documents.