Work With Configuration In ASP.NET Core

This sample json specifies some application information with some resources/files and pictures locations. We need to use this custom configuration values in our WebAPI end point. As we know there is a default controller created by the template, we can access those values from that controller.

In the startup class, there is a configuration root created at the end of the startup (the below line)

This is the class that needs to be available everywhere to access those values inside the JSON file. To make this available into the controllers, we have to inject this configuration for each controller. We can add this as a singleton class because we don’t want a separate instance for each controller. Add the below line in ConfigureServices method in startup class.

So, this makes a configuration object available for all the controllers wherever it is referred in the constructor. To understand better let’s add the below code in values controller.

Here we added a configuration parameter to the constructor and created a class level property _configuration that can be used as an endpoint. Initialized the property in the constructor and using that configuration object we can access the configuration values. We have a method called GetValue where we can specify the type of element value being retrieved and the key. As we know configuration system supports hierarchical elements we can access the multi level elements as shown above. For demonstration purpose, the values are displayed on the browser. In real time, we will be using this configuration values to perform any business logic/connecting to a server. Once you run the application the output should look like below.



This is about reading simple properties from configuration files. Another interesting feature of configuration system is, it supports reading entire section into POCO class. This can be achieved by something called IOptions. Let see the below example to work with IOptions.

To Configure options we should add another NuGet Package called Microsoft.Extensions.Options.ConfigurationExtensions. And also we need to tell the dependency injection system which section of the configuration file need to be used to create a RunMode class. It’s a kind of mapping between class and configuration section. Let's add the below line in ConfigurationServices method in startup class.

I have already created a RunMode class for mapping the configuration values. The RunMode class should look like below,

Now, let's go back to the controller and inject a parameter into the constructor IOptions<RunMode> runModeInstance. So, this option class will provide as a runModeInstance and it (ie IOptions) has a property called Value which holds the actual POCO class. After adding this IOptions to the values controller constructor should looks like below,

Once you instantiated the endpoint with Options, we can directly access configuration values as properties to an object as shown below.

So, this is the new configuration system in ASP.NET Core / .NET Core. For more details about how to work with Console based commandLine and InMemory Collection etc. in configuration system in ASP.NET core, please go through the Microsoft official website. If you are not able to understand those options, please drop a comment or message to me and I will prepare a new article for you with those features like CommandLine, InMemory, Web.Config, and IOptionsSnapshot etc.