What is the use case of IOptions versus IConfiguration (other than IOptions allows mapping to object)?

Question

I can inject the IConfiguration config into constructor and then access the app settings from json file via config["settignName"];

Example code inside service class:

public MyService(IConfiguration config)
        {
            _key = config["MyKey"];
        }

I came across IOptions which allows to map app settings from json file to a .net object.

Example:

public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<MySettings>(Configuration.GetSection("MySettings"));
...
}

And then inject the IOption into the constructor.

What is the use case of IOptions versus IConfiguration (other than IOptions allows mapping to object)? I don't see IConfiguration being used in online examples so is that OK to be used or should I switch to IOption?

Answer 1

Don't inject the whole IConfiguration interface into your service.

Injecting a class, say SmtpOptions, instead of injecting IConfiguration is a better design approach. When you inject IConfiguration, it implies that the client class (your service) will need to understand how the configuration file is structured and it will access some configuration using a key like this "Smtp:Host". So, it creates tight coupling between the client code and the configuration structure. Consequently, if the configuration file changes, you will have to change every client class.

Using IOptions (or other approaches) decouples the client class from the configuration. For example, if you decide to read the configuration from the database instead of a file, you will have only to change one piece of code which is responsible for reading and understanding the configuration file. This is much better than changing all classes that depend on IConfiguration. It is a maintenance nightmare.

Decoupling reduces applications' complexity and makes them much more maintainable.

Check this toturial https://www.youtube.com/watch?v=SizJCLcjbOA