Accessing IOptions<T> object .NET Core

Question

I am new to .NET Core and so apologies if this is a newbie question. I created a Web API project in .NET Core 2 using VS 2017.

For me, I have appsettings.json file with some connection settings.

After reading about IOptions<T> from microsoft tutorials, i am doing something like the following:

public void ConfigureServices(IServiceCollection services)
{
    services.AddOptions();
    services.Configure<MyOptions>(Configuration);

    // I want to access MyOptions object here to configure other services?how do i do that?

    service.AddHangfire( // Get MyOptions.HangfireConenctionString etc.)
}

How do I access the created MYOptions object in ConfigureServices and also if I need to access it in Configure(IApplicationBuilder app,..) method?

I only saw examples of injection IOptions<T> in controllers in the tutorials.

Answer 1

To use some settings in

public void ConfigureServices(IServiceCollection services)
{
    // Load the settings directly at startup.
    var settings = Configuration.GetSection("Root:MySettings").Get<MySettings>();

    // Verify mailSettings here (if required)

    service.AddHangfire(
        // use settings variable here
    );

    // If the settings needs to be injected, do this:
    container.AddSingleton(settings);
}

In case you require your configuration object to be used inside an application component do not inject an IOptions<T> into your component, because that only causes unforatunate downsides, as explained here. Instead, inject the value directly, as shown in the following example.

public class HomeController : Controller  
{
    private MySettings _settings;
    public HomeController(MySettings settings)
    {
        _settings = settings;
    }
}

Answer 2

You are close

services.Configure<MyOptions>(options => Configuration.GetSection("MyOptions").Bind(options));

You can now access your MyOptions using dependency injection

public class HomeController : Controller  
{
    private MySettings _settings;
    public HomeController(IOptions<MySettings> settings)
    {
        _settings = settings.Value
        // _settings.StringSetting == "My Value";
    }
}

I took the snippets from this excellent article: https://andrewlock.net/how-to-use-the-ioptions-pattern-for-configuration-in-asp-net-core-rc2/ by Andrew Lock.