Startup Filter for Settings Validation

6.Post.SettingsValidation.ConfigurationSettingValidationStartupFilter.cs

public class ConfigurationSettingValidationStartupFilter : IStartupFilter
{
	private readonly IEnumerable<ConfigurationSettings> _configurationSettings;
	private readonly ILogger<ConfigurationSettingValidationStartupFilter> _logger;

	public ConfigurationSettingValidationStartupFilter(
		IEnumerable<ConfigurationSettings> configurationSettings,
		ILogger<ConfigurationSettingValidationStartupFilter> logger)
	{
		_configurationSettings = configurationSettings;
		_logger = logger;
	}

	public Action<IApplicationBuilder> Configure(Action<IApplicationBuilder> next)
	{
		foreach (var settings in _configurationSettings)
		{
			if (settings.Validate())
			{
				continue;
			}

			var settingsName = settings.GetType().Name;
			var message = $"Invalid {settingsName} configuration. {string.Join(",", settings.ValidationResult)}";
			var exception = new InvalidOperationException(message);

			_logger.LogError(exception, "Invalid configuration. The application initialisation is aborted.");

			throw exception;
		}

		return next;
	}
}

7.Post.SettingsValidation.ConfigureOptionsExtensions.cs

public static class ConfigureOptionsExtensions
{
	public static IServiceCollection RegisterSettings<TOptions>(this IServiceCollection services, IConfiguration configuration)
		where TOptions : class, new()
	{
		var name = typeof(TOptions).Name;

		services.Configure<TOptions>(configuration.GetSection(name));
		services.AddSingleton(resolver => resolver.GetRequiredService<IOptions<TOptions>>().Value as ConfigurationSettings);

		return services;
	}
}