Umbraco-CMS/src/Umbraco.Core/DependencyInjection/ServiceCollectionExtensions.cs

using System;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Umbraco.Cms.Core.Composing;

namespace Umbraco.Extensions
{
    public static class ServiceCollectionExtensions
    {
        /// <summary>
        /// Adds a service of type <typeparamref name="TService"/> with an implementation type of <typeparamref name="TImplementing"/> to the specified <see cref="IServiceCollection"/>.
        /// </summary>
        /// <remarks>
        /// Removes all previous registrations for the type <typeparamref name="TService"/>.
        /// </remarks>
        public static void AddUnique<TService, TImplementing>(
            this IServiceCollection services,
            ServiceLifetime lifetime = ServiceLifetime.Singleton)
            where TService : class
            where TImplementing : class, TService
        {
            services.RemoveAll<TService>();
            services.Add(ServiceDescriptor.Describe(typeof(TService), typeof(TImplementing), lifetime));
        }

        /// <summary>
        /// Adds services of types <typeparamref name="TService1"/> &amp; <typeparamref name="TService2"/> with a shared implementation type of <typeparamref name="TImplementing"/> to the specified <see cref="IServiceCollection"/>.
        /// </summary>
        /// <remarks>
        /// Removes all previous registrations for the types <typeparamref name="TService1"/> &amp; <typeparamref name="TService2"/>.
        /// </remarks>
        public static void AddMultipleUnique<TService1, TService2, TImplementing>(
            this IServiceCollection services,
            ServiceLifetime lifetime = ServiceLifetime.Singleton)
            where TService1 : class
            where TService2 : class
            where TImplementing : class, TService1, TService2
        {
            services.AddUnique<TService1, TImplementing>(lifetime);
            services.AddUnique<TService2>(factory => (TImplementing)factory.GetRequiredService<TService1>(), lifetime);
        }

        // TODO(V11): Remove this function.
        [Obsolete("This method is functionally equivalent to AddSingleton<TImplementing>() please use that instead.")]
        public static void AddUnique<TImplementing>(this IServiceCollection services)
            where TImplementing : class
        {
            services.RemoveAll<TImplementing>();
            services.AddSingleton<TImplementing>();
        }

        /// <summary>
        /// Adds a service of type <typeparamref name="TService"/> with an implementation factory method to the specified <see cref="IServiceCollection"/>.
        /// </summary>
        /// <remarks>
        /// Removes all previous registrations for the type <typeparamref name="TService"/>.
        /// </remarks>
        public static void AddUnique<TService>(
            this IServiceCollection services,
            Func<IServiceProvider, TService> factory,
            ServiceLifetime lifetime = ServiceLifetime.Singleton)
            where TService : class
        {
            services.RemoveAll<TService>();
            services.Add(ServiceDescriptor.Describe(typeof(TService), factory, lifetime));
        }

        /// <summary>
        /// Adds a singleton service of the type specified by <paramref name="serviceType"/> to the specified <see cref="IServiceCollection"/>.
        /// </summary>
        /// <remarks>
        /// Removes all previous registrations for the type specified by <paramref name="serviceType"/>.
        /// </remarks>
        public static void AddUnique(this IServiceCollection services, Type serviceType, object instance)
        {
            services.RemoveAll(serviceType);
            services.AddSingleton(serviceType, instance);
        }

        /// <summary>
        /// Adds a singleton service of type <typeparamref name="TService"/> to the specified <see cref="IServiceCollection"/>.
        /// </summary>
        /// <remarks>
        /// Removes all previous registrations for the type type <typeparamref name="TService"/>.
        /// </remarks>
        public static void AddUnique<TService>(this IServiceCollection services, TService instance)
            where TService : class
        {
            services.RemoveAll<TService>();
            services.AddSingleton(instance);
        }

        internal static IServiceCollection AddLazySupport(this IServiceCollection services)
        {
            services.Replace(ServiceDescriptor.Transient(typeof(Lazy<>), typeof(LazyResolve<>)));
            return services;
        }
    }
}