Setting ASP .Net Core Environment in IIS for each App Pool without resorting to web.config changes

For when you don't want to set the environment variable in the web.config file, because that gets deployed.

Go into configuration editor

In the section choose system.webServer/aspNetCore

and then in the From drop down choose the ApplicationHost.config option

There you can add environmentVariables which need to be

ASPNETCORE_ENVIRONMENT

and

Development or Production