Almost all ASP.NET Web Applications require some sort of configuration settings to be stored in the web.config files. These settings can be application settings, database connection strings, user authentication settings, page specific settings and so on. ASP.NET also provides very powerful Configuration API to work with configuration settings defined in web.config files. The Configuration API not only allows us to read/write settings in configuration files with ease but also allow us to define our own custom configuration sections in web.config. These custom sections are very useful in large web applications where you have a lot of application settings to store in the configuration file. In this tutorial, I will show you how to create and use custom configuration sections in ASP.NET.