How I messed up
I had an ASP.NET Core WebApi project that I simply upgraded to .NET Core 2.0 by changing a line in the configuration from
Visual Studio (2017) pretty much hanged and/or performed extremely slowly. When loading the solution VS took about 2 minutes to load the web project.
How did I resolve it
Simply recreate the web project (with 2.0 selected) and import all files to it again. Pay a little notice to the startup.cs file. You might find some small changes there so don't just overwrite it.