Why do Visual Studio solutions need to be upgraded with every release of Visual Studio?

Question

This is easily one of the most annoying "features" of Visual Studio in its history and I don't understand why it exists -- ever.

Why would a CodePlex project need to care what version of Visual Studio I am using?

Off the top of my head, the only thing I can think of is that some versions of Visual Studio might introspect assemblies searching for attributes to determine what to display in "Visual Designers" and "Property Editors". But why would that cause Visual Studio to not be able to open the project and allow me to browse its contents and compile?

It seems to me like Open Source in .NET is somewhat limited by the stupid dependency management exhibited by Visual Studio. In other words, if I am using Visual Studio 2008 and you are using Visual Studio 2010, then we have different solution files.

Answer 1

http://blogs.msdn.com/b/visualstudio/archive/2010/03/15/why-does-visual-studio-2010-convert-my-projects.aspx

Here's an example from the site as to why Visual Studio converts your projects to 2010 format.

For instance, Visual Studio runs custom tools such as single file generators for designers in order to output code representing the changes made to the designer. Many of these custom tools are upgraded or completely replaced in the newer IDE. During conversion, the IDE knows which custom tools to replace or upgrade. In order to make round-tripping work, VS would need old and new custom tools to understand each other so as to ensure that old and new designers can work side by side. Other than designers, the following files would also be affected: resource editors, wizards, code snippets, item and project templates, diagramming and modeling tools, and many more.tools, and many more.

Since 2010 knows about what tools 2008 has, it can convert forward to be compatible with the custom tools 2010 uses. 2008 has no idea about what 2010 is using, how could it? Therefore, it is impossible to convert backwards since it doesn't know what it needs to convert, nor how to.

Answer 2

I believe the purpose of this touches on what you stated in your comments. If you are using 2008 and I 2010 and I compile it, how could you possibly run it again? 2010 is backwards compatible but 2008 has no way to make itself forward compatible.

Thus, by recompiling the project in 2010 I ensure that no 2008 user may mistakenly think they can compile it.