I'm on a hackathon today where we are looking at retrofitting some DevOps principles to an existing ASP.net 4.5 web application.
I learnt something about app settings which I did not know so thought I'd share it.
Settings in ASP.net
In ASP.net, the easiest way to store application settings is in the Web.Config file under the appSettings section. This is a key/value pair and is great for storing things like API urls, settings and other things that affect your app's behaviour.
In you code, you can easily access the settings from Web.Config via ConfigurationManager.AppSettings.
Settings in Azure Web App
If you host your website in an Azure Web App, there is a really neat feature that that lets you add settings at the web app level which overwrite the settings from Web.Config at runtime. You configure these in the 'application settings' menu for your web app in the Azure portal.
If a setting is absent in Azure, then the application will default back to what is in the Web.Config.
This allow you to do really useful things like use a local API for dev/test but use a production API in production without changing your code.
Hope that helps someone