Keep IIS express running
It may happen that the IIS express will close when the debug mode is turned off. This is a setting that can be changed on the project. Simply turn off "Enable edit and Continue" option, shown in picture below.
Problem with MetaData File not found .dll
"Metadata file 'C:\Projects\XYZ.dll' could not be found"
If you check the "output" tab instead, sometimes it give you extra information, like mine:
could not be resolved because it was built against the ".NETFramework,Version=v4.5.2" framework. This is a higher version than the currently targeted framework ".NETFramework,Version=v4.5.1".
Make sure that your project depends on the same version of .net, and change it to the lower one if needed.
Solution or project compile but still shows red markings
This seems to be due to some saved files... you need to remove:
1. .vs folder (it is hidden) in the root solution.
2. Delete temporary ASP.net files (C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root)
Restart Visual Studio.