ActivatorUtilities.CreateInstance用于各种激活器服务的帮助程序代码。

    public class Program
    {
        public static void Main()
        {
            ServiceCollection serviceDescriptors = new();
            var pr = serviceDescriptors.AddScoped<ServiceA>().BuildServiceProvider();
            var serviceB = ActivatorUtilities.CreateInstance<ServiceB>(pr, TypeEn.A);
            serviceB.ShowType();

            serviceB = ActivatorUtilities.CreateInstance<ServiceB>(pr, TypeEn.B);
            serviceB.ShowType();
        }


        public enum TypeEn
        {
            A,
            B
        }

        public class ServiceA
        {
        }

        public class ServiceB
        {
            public TypeEn Type { get; set; }
            public ServiceA A { get; set; }
            public ServiceB(ServiceA a, TypeEn type)
            {
                this.A = a;
                this.Type = type;
            }

            public void ShowType()
            {
                System.Console.WriteLine(Type);
            }
        }
    }