Why is "Set as Startup" option stored in the suo file and not the sln file?

Solution 1:

It is absolutely necessary that everyone can define their StartUp Project themselves, as Jon has already said. But to have a dedicated default one would be great, and as I can tell, it is possible!

If you don’t have a .suo file in your solution directory, Visual Studio picks the first project in your .sln file as the default startup project.

1. Close your Visual Studio and open the .sln file in your favorite text editor. Starting in line 4, you see all your projects encapsulated in Project – EndProject lines.

2. Cut and paste the desired default startup project to the top position.

3. Delete your .suo file.

4. Open your solution in Visual Studio. Ta daa!

Solution 2:

In most cases, it does make sense to have a default on this.

It would be much better to accommodate a default startup project and store this in the .sln file, but which can be overridden by a developer in their .suo file. If the startup setting isn’t found in the .suo file, the default startup project in the .sln would be used.

Actually, this has been suggested on Visual Studio’s UserVoice.

Solution 3:

Why should it be a non-user-specific preference?

If I've got a solution with 10 files in, and one developer is primarily testing/using one of those tools, why should that affect what I start up?

I think MS made the right choice on this one. The project I want to start is far from necessarily the project that other developers want to start.