仿照 MediatR实现了一个中介者模式Publish功能，使用同MediatR

• 接口和实现

　　public interface IMediator
    {
        Task Publish<T>(T notification, CancellationToken cancellationToken = default) where T : class, INotification;
    }

    public class Mediator : IMediator
    {
        private IServiceProvider _serviceProvider;
        private static ConcurrentDictionary<Type, Func<INotification, CancellationToken, Task>> _handle = new ConcurrentDictionary<Type, Func<INotification, CancellationToken, Task>>();
        public Mediator(
            IServiceProvider serviceProvider
            )
        {
            _serviceProvider = serviceProvider;
        }
        public Task Publish<T>(T notification, CancellationToken cancellationToken = default) where T : class, INotification
        {
            notification.IsNull("notification is null");
            var notificationType = notification.GetType();
            var func = _handle.GetOrAdd(notificationType, type =>
            {
                Func<INotification, CancellationToken, Task> handle = null;
                var handles = _serviceProvider.GetServices(typeof(INotificationHandler<T>));
                foreach (var item in handles)
                {
                    var generic = item.GetType().GetInterface($"{nameof(INotificationHandler<INotification>)}`1").GetGenericArguments().First();

                    if (!generic.Name.Equals(type.Name)) continue;
                    if (item is INotificationHandler<T> h )
                    {
                        handle += (x, y) => {

                           return  h.Handle((T)x,y);
                        };
                    }
                }
                return handle;
            });
            if (func == null) throw new Exception(message: $"对应的 INotificationHandler<{notificationType.Name}>的实现没有注入");
            return func((INotification)notification, cancellationToken);
        }
    }

•  INotification 空接口

　　 public interface INotification
    {
    }

• INotificationHandler<T>接口

    public interface INotificationHandler<T> where T : INotification 
    {
        Task Handle(T notification, CancellationToken cancellationToken=default(CancellationToken));
    }

• 其他代码

    public static class CheckNull
    {
        public static void IsNull<T>(this T t,  string message="") 
        {
            if (t == null)
            {
                throw new ArgumentNullException(nameof(t), message);
            }
        }
    }

• 注入

    service.AddSingleton<IMediator, Mediator>();
    service.AddSingleton<INotificationHandler<MsgMonitorEvent>, MsgMonitorEventHandler>();
    service.AddSingleton<INotificationHandler<MsgMonitorEvent>, MsgMonitorNoticeHandler>();

• Handler接口实现

     public class 
    MsgMonitorNoticeHandler:INotificationHandler<MsgMonitorEvent>
    {
        public async Task Handle(MsgMonitorEvent notification, CancellationToken cancellationToken = default)
        {
            Console.WriteLine("测试赛");
            await Task.CompletedTask;
        }
    }

• 实现接口INotification的对象

    public class MsgMonitorEvent:INotification
    {
        public List<PerformancMonitorDto<MsgMonitorDto>> MonitorDtos { get; set; }
    }

• 使用和MediatR完全一样，这样做的目的是不想代码中有太多依赖，可以在任意版本中切换重新编译可立即使用，2.1  3.1  5  6