Get the InstrumentationKey currently in ApplicationInsights.config from web.config or Portal App Settings
Full App Insights functionality depends on the InstrumentationKey being specified in a file called ApplicationInsights.config deployed to the root of the application. On deployment, it's difficult to transform the app insights config file with the application insights instrumentation key used by the application.
I suggest that Application Insights, instead of pulling the instrumentation key from the ApplicationInsights.config file, get the instrumentation key from the portal application settings, from the APPINSIGHTS_INSTRUMENTATIONKEY, for example.
This would avoid Release Engineers from having to manually edit the ApplicationInsights.config file on every release to an environment. If they neglect to do this, one could end up with a Production environment pushing logs to a developer's Application Insights instance.