Asp.Net Core Configuration

Configuration settings is an important part of any large application. We will have to store and use various config settings like connection string, file path etc in an application. In the older version of Asp.Net Applications configuration settings were stored in web.config files which is an XML file. The System.Configuration namespace was used to read key-value pairs from XML configuration file web.config.

Asp.Net Core provides various options to store and retrieve configuration settings. Following are some of the options provided by Asp.Net Core to store and retrieve configuration settings.

Configuration Settings files like appsettings.json (JSON, XML or INI files are supported)

Azure Key Vault

Command-line arguments

Environment variables

In-memory .NET objects

Custom providers
In .Net Core, the Microsoft.Extensions.Configuration library is used to read settings from the various configuration options.

Before the app is configured and started, a host is configured and launched. The host is responsible for app startup and lifetime management. Web apps based on the ASP.NET Core call CreateDefaultBuilder when building a host. Host configuration can be specified in environment variables prefixed with ASPNETCORE_. The prefix (ASPNETCORE_) is stripped when the configuration key-value pairs are loaded.