This has had a few twists and turns. I've modified this answer to be up to date with ASP.NET Core 2.0 (as of 26/02/2018).
This is mostly taken from the official documentation:
To work with settings in your ASP.NET application, it is recommended that you only instantiate a Configuration in your application’s Startup class. Then, use the Options pattern to access individual settings. Let's say we have an appsettings.json file that looks like this:
{ "MyConfig": { "ApplicationName": "MyApp", "Version": "1.0.0" } }
And we have a POCO object representing the configuration:
public class MyConfig { public string ApplicationName { get; set; } public int Version { get; set; } }
Now we build the configuration in Startup.cs:
public class Startup { public IConfigurationRoot Configuration { get; set; } public Startup(IHostingEnvironment env) { var builder = new ConfigurationBuilder() .SetBasePath(env.ContentRootPath) .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true); Configuration = builder.Build(); } }
Note that appsettings.json will be registered by default in .NET Core 2.0. We can also register an appsettings.{Environment}.json config file per environment if needed.
If we want to inject our configuration to our controllers, we'll need to register it with the runtime. We do so via Startup.ConfigureServices:
public void ConfigureServices(IServiceCollection services) { services.AddMvc(); // Add functionality to inject IOptions<T> services.AddOptions(); // Add our Config object so it can be injected services.Configure<MyConfig>(Configuration.GetSection("MyConfig")); }
And we inject it like this:
public class HomeController : Controller { private readonly IOptions<MyConfig> config; public HomeController(IOptions<MyConfig> config) { this.config = config; } // GET: /<controller>/ public IActionResult Index() => View(config.Value); }
The full Startup class:
public class Startup { public IConfigurationRoot Configuration { get; set; } public Startup(IHostingEnvironment env) { var builder = new ConfigurationBuilder() .SetBasePath(env.ContentRootPath) .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true); Configuration = builder.Build(); } public void ConfigureServices(IServiceCollection services) { services.AddMvc(); // Add functionality to inject IOptions<T> services.AddOptions(); // Add our Config object so it can be injected services.Configure<MyConfig>(Configuration.GetSection("MyConfig")); } }
