.net core實現批量依賴注入

　　最近在做公司老項目升級，要將原有的.net framework程序，升級到.net core平台，這個過程中就發現了一個問題，老項目在調用Service或者是Repository的時候都是直接new出來的，這顯然不符合我們.net core的規范，在.net core里邊更推薦用依賴注入，這就犯難了，如果我每個Service或者是Repository都在Starpup里面注冊，怕是要寫個幾百行，而且也很繁瑣。

　　今天上午，想了想要不求助一下大佬 @7thiny ，經過大佬的幫助，寫了一個用於全局注冊的方法，代碼如下：

public static class InjectHelper
    {
        /// <summary>
        /// Add Scoped from InterfaceAssembly and ImplementAssembly to the specified Microsoft.Extensions.DependencyInjection.IServiceCollection.
        /// </summary>
        /// <param name="services"></param>
        /// <param name="interfaceAssembly"></param>
        /// <param name="implementAssembly"></param>
        public static void AddScoped(this IServiceCollection services, Assembly interfaceAssembly, Assembly implementAssembly)
        {
            var interfaces = interfaceAssembly.GetTypes().Where(t => t.IsInterface);
            var implements = implementAssembly.GetTypes();
            foreach (var item in interfaces)
            {
                var type = implements.FirstOrDefault(x => item.IsAssignableFrom(x));
                if (type != null)
                {
                    services.AddScoped(item, type);
                }
            }
        }

        /// <summary>
        /// Add AddSingleton from InterfaceAssembly and ImplementAssembly to the specified Microsoft.Extensions.DependencyInjection.IServiceCollection.
        /// </summary>
        /// <param name="services"></param>
        /// <param name="interfaceAssembly"></param>
        /// <param name="implementAssembly"></param>
        public static void AddSingleton(this IServiceCollection services, Assembly interfaceAssembly, Assembly implementAssembly)
        {
            var interfaces = interfaceAssembly.GetTypes().Where(t => t.IsInterface);
            var implements = implementAssembly.GetTypes();
            foreach (var item in interfaces)
            {
                var type = implements.FirstOrDefault(x => item.IsAssignableFrom(x));
                if (type != null)
                {
                    services.AddSingleton(item, type);
                }
            }
        }

        /// <summary>
        /// Add AddTransient from InterfaceAssembly and ImplementAssembly to the specified Microsoft.Extensions.DependencyInjection.IServiceCollection.
        /// </summary>
        /// <param name="services"></param>
        /// <param name="interfaceAssembly"></param>
        /// <param name="implementAssembly"></param>
        public static void AddTransient(this IServiceCollection services, Assembly interfaceAssembly, Assembly implementAssembly)
        {
            var interfaces = interfaceAssembly.GetTypes().Where(t => t.IsInterface);
            var implements = implementAssembly.GetTypes();
            foreach (var item in interfaces)
            {
                var type = implements.FirstOrDefault(x => item.IsAssignableFrom(x));
                if (type != null)
                {
                    services.AddTransient(item, type);
                }
            }
        }
    }

　　這樣我們就可以通過丟兩個Assembly進去，來幫助我們批量注冊服務，在Startup中調用方法如下：

            services.AddScoped(Assembly.Load("xxxx.IService"), Assembly.Load("xxxx.Service"));
            services.AddScoped(Assembly.Load("xxxx.IService"), Assembly.Load("xxxx.Service"));