Revert the context sensitive help to the old MSDN site where docs.microsoft.com isn't ready
I've been finding the context sensitive help in VS 2017 generally woeful. In earlier versions it used to be so good, but now most of the time it just looks like auto-generated documentation that gives basically no more than you can get from intellisense.
I can understand the ASP.Net Core documentation lagging, although even in that case there looks to be a major under investment. It's a great technology, but it can be really hard to learn without a lot, a lot, of googling.
But for the older technology (e.g. .Net full framework), there must be the existing documentation locked away somewhere but no longer accessible.
I've attached a couple of screenshots - one for context sensitive help (F1) on IHostingEnvironment in a ASP.Net Core 2.0 project, the other for Path.IsPathRooted in a .Net 4.6.1 project.