Why and when should I ever be using .sln files?

Question

I understand that a solution file contains a group of other projects but why would I ever want to have a group of projects in a single file? The company I work at uses this frequently however I am not seeing why.

Another thing I noticed is that you can run a .sln file but what is happening when the file is being executed? What did it just do?

So my main question is why store multiple projects in a single .sln file rather than simply do all of the work in just one project?

Answer 1

but why would I ever want to have a group of projects in a single file?

Because you are not a hobby programmer just learning to program and writing hello world like applications.

My main project has around 40 projects that belong to one application. A shell, multiple powershell extensions, multiple programs, multiple installers. They belong together and get built together - they are one solution.

Another thing I noticed is that you can run a .sln file but what is happening when the file is being executed?

MSBuild builds the projects as per instructions in the solution, what else?

Answer 2

Quote from some extract of MSDN

Visual Studio provides two containers to help you efficiently manage the items that are required by your development effort, such as references, data connections, folders, and files. These containers are called solutions and projects. You use Solution Explorer to view and manage projects and solutions and their associated items.

Solutions contain items that you need in order to create your application. A solution includes one or more projects, plus files and metadata that help define the solution as a whole. Visual Studio automatically generates a solution when you create a new project. Visual Studio stores the definition for a solution in two files: .sln and .suo. The solution definition file (.sln) stores the metadata that defines your solution, including:

• The projects that are associated with the solution.
• The items that are not associated with a particular project.
• The build configurations that determine which project configurations to apply in each type of build.

The metadata stored in the .suo file as you construct a solution and set its properties is used to customize the IDE whenever the solution is active. For example, Solution Explorer displays a Miscellaneous Files folder for a solution if you enable that option, and tools appropriate for the types of projects included in the solution become available from the Toolbox.

Answer 3

The point is because, as you write more and more complex applications, you will see that these complex applications will need to be broken up into pieces. For example, you might have an application that accesses a database. The database project might be separate. The reason being is because you may want to use this database with another application. If the data layer api was not separate, you couldn't do this.

There are several reasons to have multiple projects. Here is a few:

1. Code reusability. You might have designed some code that you want to package into a library and reuse with other programs in the future.

2. Simplicity. Sometimes when creating a complex application, you'll want to architect things in pieces, so the application is easier to debug, as a whole.

3. Conflicting languages. Supposed your application is written in C#, but you want to use some code thats contained in a VB.NET library. Since a project cannot mix C# and VB.NET code, your solution is to create different projects in the same solution.

Answer 4

Reasons you might want multiple projects in a single solution:

• Different projects can have different dependencies (either dependencies to other projects in your solution, or commonly, dependencies to third-party dlls.)
• Different projects can be different types - console app, dll, web service, etc.
• Different projects can have different pre/post-build steps
• Some of your projects might not even be implemented in C#. You can have c++, VB.net, etc., projects in the same solution as well.
• Different projects might be components that are reused by various other teams.
• many other reasons

Thus, it makes sense to be able to group multiple projects together, such that you can open the whole group, hit compile to compile all of the projects in the appropriate order (which can be important, if for instance, one of your projects builds a dll that another project requires as a dependency), then launch any of them that you specify.

When you open the solution, that's all it does: opens each of the projects contained in the solution in a single Visual Studio window, along with metadata about how to compile the solution, which project should be launched when you hit Run, etc.

Answer 5

Here's a concrete example:

If you split some of your logic out of your project into a re-usable library then that would be a second project (class library), you can then reference that from the first project by name if they are contained in the same solution. And when you run your project the second project will automatically be rebuilt as necessary by visual studio.

Answer 6

Its is easier to group your projects together within a solution because whenever you open the solution, all files needed for that project to run will be opened as well.

It also makes it much easier to create one 'solution' for one portion of a program, and then add that solution to the master solution the contains the entire program. This makes it easy to compartmentalize your code, and know which pieces are dependent on others.

What method were you previously using to organize your projects?

Answer 7

When you double click on the .sln (solution) file, it will open that solution in Visual Studio.

A solution allows you to group projects together in a single, erm, solution.