How to get the list of IOptions available from DI in c# Core?

Question

Following this post: https://blog.bredvid.no/validating-configuration-in-asp-net-core-e9825bd15f10

I m now available to validate the Settings when a service need it.

Answer 1

You can get a list of configured option types by iterating the IServiceCollection instance:

var configuredOptionTypes =
    from descriptor in services
    let serviceType = descriptor.ServiceType
    where serviceType.IsGenericType
    where serviceType.GetGenericTypeDefinition() == typeof(IConfigureNamedOptions<>)
    let optionType = serviceType.GetGenericArguments()[0]
    select optionType;

Answer 2

Following suggestions from Steven, here is my solution: My settings validator service

    public SettingsValidator(
        IServiceProvider services,
        ILifetimeScope scope
    )
    {
        var types = scope.ComponentRegistry.Registrations
            .SelectMany(e => e.Services)
            .Select(s => s as TypedService)
            .Where(s => s.ServiceType.IsAssignableToGenericType(typeof(IConfigureOptions<>)))
            .Select(s => s.ServiceType.GetGenericArguments()[0])
            .Where(s => typeof(ISettings).IsAssignableFrom(s))
            .ToList();

        foreach (var t in types)
        {
            var option = services.GetService(typeof(IOptions<>).MakeGenericType(new Type[] { t }));
            option.GetPropertyValue("Value");
        }
    }

in startup:

        builder.RegisterType<SettingsValidator>();

example of Settings

public class AzureStorageSettings : ISettings
{
    [Required]
    public string ConnectionString { get; set; }
    [Required]
    public string Container { get; set; }
    [Required]
    public string Path { get; set; }
}

extensions

public static class TypeExtensions
{
    public static bool IsAssignableToGenericType(this Type givenType, Type genericType)
    {
        foreach (var it in givenType.GetInterfaces())
        {
            if (it.IsGenericType && it.GetGenericTypeDefinition() == genericType)
                return true;
        }

        if (givenType.IsGenericType && givenType.GetGenericTypeDefinition() == genericType)
            return true;

        Type baseType = givenType.BaseType;
        if (baseType == null) return false;

        return IsAssignableToGenericType(baseType, genericType);
    }
}

in program.cs

using (var scope = webHost.Services.CreateScope())
        {
            var services = scope.ServiceProvider;
            var logger = services.GetRequiredService<ILogger<Program>>();
            try
            {
                logger.LogInformation("Starting settings validation.");
                services.GetRequiredService<SettingsValidator>();
                logger.LogInformation("The settings have been validated.");
            }
            catch (Exception ex)
            {
                logger.LogError(ex, "An error occurred while validating the settings.");
            }
        }

Let me know if it works for you too :)