.NET Core-IServiceCollection扩展一个Replace方法

Replace方法可替换掉之前注入的服务，比如我们可以替换框架中用到的服务，达到修改源码的目的

    public static class ServiceCollectionExtensions
    {
        public static IServiceCollection Replace<TService, TImplementation>(this IServiceCollection services)
            where TImplementation : TService
        {
            return services.Replace<TService>(typeof(TImplementation));
        }

        public static IServiceCollection Replace<TService>(this IServiceCollection services, Type implementationType)
        {
            return services.Replace(typeof(TService), implementationType);
        }

        public static IServiceCollection Replace(this IServiceCollection services, Type serviceType, Type implementationType)
        {
            if (services == null)
            {
                throw new ArgumentNullException(nameof(services));
            }

            if (serviceType == null)
            {
                throw new ArgumentNullException(nameof(serviceType));
            }

            if (implementationType == null)
            {
                throw new ArgumentNullException(nameof(implementationType));
            }

            if (!services.TryGetDescriptors(serviceType, out var descriptors))
            {
                throw new ArgumentException($"No services found for {serviceType.FullName}.", nameof(serviceType));
            }

            foreach (var descriptor in descriptors)
            {
                var index = services.IndexOf(descriptor);

                services.Insert(index, descriptor.WithImplementationType(implementationType));

                services.Remove(descriptor);
            }

            return services;
        }

        private static bool TryGetDescriptors(this IServiceCollection services, Type serviceType, out ICollection<ServiceDescriptor> descriptors)
        {
            return (descriptors = services.Where(service => service.ServiceType == serviceType).ToArray()).Any();
        }

        private static ServiceDescriptor WithImplementationType(this ServiceDescriptor descriptor, Type implementationType)
        {
            return new ServiceDescriptor(descriptor.ServiceType, implementationType, descriptor.Lifetime);
        }
    }