FunctionalNamedServiceProviderDemo

FunctionalNamedServiceProviderDemo.cs

private static class ServiceBuilder
{
    private static readonly Lazy<IServiceProvider> Instance = new Lazy<IServiceProvider>(GetServiceProvider);

    public static IServiceProvider Get() => Instance.Value;

    private static IServiceProvider GetServiceProvider()
    {
        var services = new ServiceCollection();

        services.AddSingleton<KelvinConverterMapper>(provider => (tempScale, temp) =>
        {
            switch ((string.IsNullOrEmpty(tempScale) ? " " : tempScale).ToUpper()[0])
            {
                case 'C':
                    return CentigradeToKelvins(temp);

                case 'F':
                    return FahrenheitToKelvins(temp);

                case 'R':
                    return RankineToKelvinMapper(temp);

                case 'K':
                    return KelvinsToKelvins(temp);

                default:
                    throw new KeyNotFoundException($"Unknown scale '{tempScale}'");
            }

        });

        services.AddSingleton<TemperatureCalculator>();

        return services.BuildServiceProvider();
    }

    private static decimal CentigradeToKelvins(decimal value) => value + 273.15M;
    private static decimal FahrenheitToKelvins(decimal value) => (value + 459.67M) * 5 / 9;
    private static decimal RankineToKelvinMapper (decimal value) => value * 5 / 9;
    private static decimal KelvinsToKelvins(decimal value) => value;
    
}