We routinely run into cases where the new project system and ASP.NET MVC 5 collide (or rather, don't) - I'd like to see support added. Here are the main use cases I'm aware of, I hope others add more to this issue:

Use Case: Migration

One of the awesome features of the new .csproj system is glob patterns (and Visual Studio not replacing them on every save). This was something we really looked forward to as a real time saver and merge reducer, but in practice we can't use the new project system because a lot of functionality for ASP.NET MVC 5 apps is missing, e.g. even hitting F5 to run it.

When we migrate a large solution to ASP.NET Core, it's a stop-the-world endeavor as are most major changes. Swapping any fundamental framework piece will need to be a big swap, so you want to reduce that window and risk as much as possible. In the case of ASP.NET to ASP.NET Core, you need to swap the project file, all references, port controllers, views, etc. This is a lot to do at once, and every change since you started that path is a royal pain.

A large part of this pain is in the project file itself, since nearly every commit adding or removing files is a merge conflict. And when moving from non-glob to blog worlds, it's a huge pain to manually sync everything into that major change branch.

But why not just stay on non-globs until after the move?

Again, merge pain. A large change like this necessitates moving files around quite a bit and that's the same merge pain between users as exists in 1 world today.

Use Case: Library Projects

We also have several projects that need to support ASP.NET and ASP.NET Core, there are hundreds of thousands of users on the old systems and we need to support them. In the ASP.NET cases specically, we need to have a ASP.NET and an ASP.NET Core sample. In all of these, the only use of the old project system is the ASP.NET (non-core) sample projects. We have to choose between:

• Leave it as the old project system, managing both in different ways forever.
• Screw it, upgrade and host it in IIS, manually attach debuggers, etc.

Adding support for ASP.NET MVC 5 projects for example would help tremendously in porting to ASP.NET Core. In our case, it'd help now for library projects (needed dependencies for main websites to move), and later for those sites like Stack Overflow. We've been working on the .NET Core story for quite a while now, but the daunting task of upgrading the main applications would be made much easier if we could get on the new project system first.

For today examples, I'm using the new .csproj in MiniProfiler and Exceptional MVC 5 Sample projects. The upside is management and simplicity, the downside is users constantly asking why F5 doesn't work. At the moment I'm considering changing them to the old system since the main point of a sample is a bit missed when they can't test it.

Use Case: Immediate

Additionally, it'd just make life easier today in itself, apart from upgrade reasons, by:

• Eliminating most of the cases we run into merge conflicts today
• Make git history usable (e.g. when did we upgrade library X?)
• Reducing project and solution reloads
• Not restarting Visual Studio constant because of the above (this is still faster than reload in VS 2017)

Can we please consider adding support for these project types? Such support would make life easier both immediately and for upgrading in the future.