Using IIS Express, with Visual Studio 2015, Update 1, when trying to start a MVC 5 website I get the message:
HttpClient cannot be null.
and then the site doesn't show.
I have tried the usual tricks of "closing, deleting the suo and reopening" or "clean & rebuild".
This seems to suggest that I should reinstall Studio, but I'd really rather not.
What is causing this and how do I resolve it without a reinstall?
I don't see the symptoms in this question, nor would I like to disable diagnostic tools like this question suggests.
Moving to Update 2 solved my problem and restored the functionality of the Diagnostic Tools window.