Displaying Files By Using the Open File Command
The following steps describe how the IDE handles the Open File command, which is available on the File menu in Visual Studio. The steps also describe how projects should respond to calls that originate from this command.
When a user clicks the Open File command on the File menu, and selects a file from the Open File dialog box, the following process occurs.
Using the running document table, the IDE determines whether the file is already open in a project.
If the file is open, the IDE resurfaces the window.
If the file is not open, the IDE calls IsDocumentInProject to query each project to determine which project can open the file.
Notes
In your project implementation of IsDocumentInProject, provide a priority value that indicates the level at which your project opens the file. Priority values are provided in the VSDOCUMENTPRIORITY enumeration.
Each project responds with a priority level that indicates the importance it places on being the project to open the file.
The IDE uses the following criteria to determine which project opens the file:
The project that responds with the highest priority (DP_Intrinsic) opens the file. If more than one project responds with this priority, the first project to respond opens the file.
If no project responds with the highest priority (DP_Intrinsic), but all projects respond with the same, lower priority, the active project opens the file. If no project is active, the first project to respond opens the file.
If no project claims ownership of the file (DP_Unsupported), the Miscellaneous Files project opens the file.
If an instance of the Miscellaneous Files project is created, the project always responds with the value DP_CanAddAsExternal. This value indicates that the project can open the file. This project is used to house open files that are not in any other project. The list of items in this project is not persisted; this project is visible in Solution Explorer only when it is used to open a file.
If the Miscellaneous Files project does not indicate that it can open the file, an instance of the project has not been created. In this case, the IDE creates an instance of the Miscellaneous Files project and tells the project to open the file.
As soon as the IDE determines which project opens the file, it calls the OpenItem method on that project.
The project then has the option of opening the file by using a project-specific editor or a standard editor. For more information, see How to: Open Project-Specific Editors and How to: Open Standard Editors, respectively.
See Also
Tasks
How to: Open Project-Specific Editors
Concepts
Displaying Files By Using the Open With Command