.net core实现批量依赖注入

　　最近在做公司老项目升级，要将原有的.net framework程序，升级到.net core平台，这个过程中就发现了一个问题，老项目在调用Service或者是Repository的时候都是直接new出来的，这显然不符合我们.net core的规范，在.net core里边更推荐用依赖注入，这就犯难了，如果我每个Service或者是Repository都在Starpup里面注册，怕是要写个几百行，而且也很繁琐。

　　今天上午，想了想要不求助一下大佬 @7thiny ，经过大佬的帮助，写了一个用于全局注册的方法，代码如下：

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);
                }
            }
        }
    }

　　这样我们就可以通过丢两个Assembly进去，来帮助我们批量注册服务，在Startup中调用方法如下：

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