Use ASP.NET Core Options with an instance

ASP.NET Core provides a built-in mechanism for configuring an application’s options using the Options pattern. This pattern allows you to define a class to represent the options you want to configure and then bind those options to values from a variety of sources, such as configuration files, environment variables or command-line arguments.

One way to use the Options pattern is to configure an object instance using the Options.Create() method. This method creates an instance of a class and assigns its properties the values from the configuration sources.

Here’s an example of how to use Options.Create() to configure an object instance in an ASP.NET Core application:

Define a class to represent the options you want to configure. This class should have properties for each option, with default values if necessary.

1public class MyOptions
2{
3    public string Option1 { get; set; } = "default value";
4    public int Option2 { get; set; } = 42;
5}

In your ASP.NET Core application’s Startup class, add the options class to the service collection using the services.Configure() method. This will allow the options to be injected into controllers and other services.

1public void ConfigureServices(IServiceCollection services)
2{
3    services.Configure<MyOptions>(Configuration);
4}

Inject an instance of the options class into a controller or service using dependency injection.

 1public class MyController : Controller
 2{
 3    private readonly MyOptions _options;
 4
 5    public MyController(IOptions<MyOptions> options)
 6    {
 7        _options = options.Value;
 8    }
 9
10    public IActionResult Index()
11    {
12        return View(_options);
13    }
14}

Use the Options.Create() method to create an instance of the options class and configure it with values from the configuration sources.

IOptions<MyOptions> myOptionsInstance = Options.Create(new MyOptions());

This will create an instance of MyOptions and assign its properties the values from the configuration sources defined in the Startup class. You can also pass an anonymous object to the Options.Create() method to override the default values for specific options.

1IOptions<MyOptions> myOptionsInstance = Options.Create(new MyOptions
2{
3    Option1 = "overridden value",
4});

This will create an instance of MyOptions with the Option1 property set to “overridden value” and the Option2 property set to its default value of 42.

Using the Options.Create() method is a convenient way to configure an object instance with values from the configuration sources in an ASP.NET Core application. It allows you to easily bind options to values from a variety of sources and inject those options into controllers and other services using dependency injection.

To use this in your dependency injection, you can just use a singleton - because that’s what services.Configure() under the hood does, too.

1public void ConfigureServices(IServiceCollection services)
2{
3    IOptions<MyOptions> myOptionsInstance = Options.Create(new MyOptions());
4    services.AddSingleton(myOptionsInstance);
5}

In conclusion, the Options pattern in ASP.NET Core provides a flexible and convenient way to configure an application’s options using a variety of sources. The Options.Create() method allows you to create an instance of a class and bind its properties to values from the configuration sources, making it easy to inject those options into controllers and other services using dependency injection. Whether you need to configure a single object instance or multiple instances with different values, the Options pattern and the Options.Create() method provide a powerful and flexible solution.