EventBus事件总线（牛x版）

成员介绍：

IEventBus、EventBus：事件总线

IEventHandler、xxxEventHandler：事件处理程序

IEvent、xxxEvent：事件，一个事件可对应多个事件处理程序

EventHandlerAttribute：事件处理程序的特性，可添加排序信息等

EvnetHandlerMetadata：IEventHandler信息

EventHandlerMetadataItem：EventHandler实例信息

事件总线：

     public interface IEventBus
     {
         void Trigger<TEvent>(TEvent eventData, string topic = null) where TEvent : IEvent;
     }
     public class EventBus : IEventBus
     {
         private static System.Collections.Concurrent.ConcurrentDictionary<Type, EvnetHandlerMetadata> _evnetHandlerMetadatas
             = new ConcurrentDictionary<Type, EvnetHandlerMetadata>();
         private static readonly EventHandlerAttribute DefaultAttribute = new EventHandlerAttribute()
         {
             IgnoreError = false,
             Priority = ,
             Topic = null
         };

         static EventBus()
         { }

         public Func<Type, object> Activator { get; set; }

         /// <summary>
         /// 触发事件
         /// </summary>
         /// <typeparam name="IEvent"></typeparam>
         /// <param name="eventData"></param>
         public void Trigger<TEvent>(TEvent eventData, string topic = null) where TEvent : IEvent
         {

             EvnetHandlerMetadata evnetHandlerMetadata = _evnetHandlerMetadatas.GetOrAdd(typeof(TEvent), (key) =>
             {
                 var handlerType = typeof(IEventHandler<>).MakeGenericType(typeof(TEvent));
                 var handlerMetadata = new EvnetHandlerMetadata()
                 {
                     EventHandlerType = handlerType,
                     EventType = key,
                     Items = new List<EventHandlerMetadataItem>()
                 };
                 var handlerInstances = Activator.Invoke(typeof(IEnumerable<>).MakeGenericType(handlerType)) as IEnumerable;
                 foreach (var handlerInstance in handlerInstances)
                 {
                     var typeInfo = handlerInstance.GetType().GetTypeInfo();
                     var handleMethods = typeInfo.DeclaredMethods.Where(t => t.Name.EndsWith($"{key.Name}>.Handle") || t.Name == "Handle");
                     var method = handleMethods.FirstOrDefault();
                     if (method == null) continue;
                     var attr = method.GetCustomAttribute<EventHandlerAttribute>()
                         ?? handlerInstance.GetType().GetCustomAttribute<EventHandlerAttribute>()
                         ?? DefaultAttribute
                         ;
                     handlerMetadata.Items.Add(new EventHandlerMetadataItem()
                     {
                         Method = method,
                         IgnoreError = attr.IgnoreError,
                         Priority = attr.Priority,
                         Type = handlerInstance.GetType()
                     });
                 }
                 handlerMetadata.Items = handlerMetadata.Items.OrderByDescending(p => p.Priority).ThenBy(x => x.Type.Name).ToList();
                 return handlerMetadata;
             });

             var handlers = evnetHandlerMetadata.Items
                 .WhereIf(p => p.Topic == topic, !string.IsNullOrEmpty(topic))
                 .Select(x => new { Instance = Activator.Invoke(x.Type), Meta = x })
                 .ToList()
                 ;
             foreach (var handler in handlers)
             {
                 try
                 {
                     handler.Meta.Method.Invoke(handler.Instance, new object[] { eventData });
                 }
                 catch (Exception ex)
                 {
                     if (!handler.Meta.IgnoreError)
                     {
                         while (true)
                         {
                             if (ex.InnerException == null)
                             {
                                 throw ex;
                             }
                             else
                             {
                                 ex = ex.InnerException;
                             }
                         }

                     }
                 }
             }
         }

         public class EventHandlerMetadataItem
         {
             public Type Type { get; set; }
             public MethodInfo Method { get; set; }
             public int Priority { get; set; }
             public bool IgnoreError { get; set; }
             public string Topic { get; set; }

         }

         public class EvnetHandlerMetadata
         {
             public List<EventHandlerMetadataItem> Items { get; set; }
             public Type EventHandlerType { get; set; }
             public Type EventType { get; set; }

         }
     }

事件处理接口：

     /// <summary>
     /// 事件处理接口
     /// </summary>
     /// <typeparam name="TEvent">继承IEvent对象的事件源对象</typeparam>
     public interface IEventHandler<T> where T : IEvent
     {
         /// <summary>
         /// 处理程序
         /// </summary>
         /// <param name="evt"></param>
         void Handle(T evt);
     }

     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
     public class EventHandlerAttribute : Attribute
     {
         /// <summary>
         /// 执行优先级
         /// </summary>
         public int Priority { get; set; }
         public bool IgnoreError { get; set; }
         public string Topic { get; set; }
         public EventHandlerAttribute()
         {

         }
     }

public interface IEvent
{
}

具体事件处理：

     /// <summary>
     /// 文件上传事件处理
     /// </summary>
     [EventHandler(Priority =, IgnoreError = true)]
     public class FileUploadEventHandler : IEventHandler<FileUploadEvent>
     {
         private readonly IFeeService _feeService;
         private readonly ILogger _logger;

         public FileUploadEventHandler(
             IFeeService feeService,
             ILogger<FileUploadEventHandler> logger
             )
         {
             _feeService = feeService;
             _logger = logger;
         }

         public void Handle(FileUploadEvent evt)
         {
            // _logger.LogInformation(evt.FileName);
             ////扣减存储空间
             //var useResult=_feeService.UseFeeItem(Enums.Finance_FeeItem.Storage, evt.FileSize, $"上传文件{evt.FileName}");
             //if (!useResult.Success)
             //{
             //    throw new Exception(useResult.Message);
             //}
         }
     }

事件触发：

var eventBus = _serviceLocator.GetService<IEventBus>();
eventBus.Trigger(new FileUploadEvent() { OwnUserID = globalValue.User.ID, UserID = globalValue.User.OwnUserID, Url = uploadResult.Data.Url, FileName = file.FileName, FileSize = file.Length, FileType = fileType });

参考：https://www.cnblogs.com/lwqlun/p/10468058.html