Solutions overview
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
A solution is a grouping of one or more projects that work together to create an application. The project and status information pertaining to the solution are stored in two different solution files. The solution (.sln) file is text-based and can be placed under source code control and shared between users. The solution user option (.suo) file is binary. As a result, the .suo file cannot be placed under source code control and contains user-specific information.
Any VSPackage can write to either type of solution file. Because of the nature of the files, there are two different interfaces implemented to write to them. The IVsPersistSolutionProps interface writes text information to the .sln file and the IVsPersistSolutionOpts interface writes binary streams to the .suo file.
Note
A project does not have to explicitly write an entry for itself into the solution file; the environment handles that for the project. Therefore, unless you want to add additional content specifically to the solution file, you do not need to register your VSPackage in this way.
Each VSPackage supporting solution persistence uses three interfaces, the IVsSolutionPersistence interface, which is implemented by the environment and called by the VSPackage, and IVsPersistSolutionProps and IVsPersistSolutionOpts, which are both implemented by the VSPackage. The IVsPersistSolutionOpts interface only needs to be implemented if private information is to be written by the VSPackage to the .suo file.
When a solution is opened, the following process takes place.
The environment reads the solution.
If the environment finds a
CLSID, it loads the corresponding VSPackage.If a VSPackage is loaded, the environment calls
QueryInterfacefor IVsPackage interface for the interface that the VSPackage requires.When reading from an .sln file, the environment calls
QueryInterfaceforIVsPersistSolutionProps.When reading from an .suo file, the environment calls
QueryInterfaceforIVsPersistSolutionOpts.
Specific information relating to the use of these files can be found in Solution (.Sln) File and Solution User Options (.Suo) File.
Note
If you want to create a new solution configuration consisting of two projects' configurations and excluding a third from the build, you need to use the Property Pages UI or automation. You can't change the solution build manager configurations and their properties directly, but you can manipulate the solution build manager using the SolutionBuild class from DTE in the automation model. For more information about configuring solutions, see Solution Configuration.