浅析Mediator

一、轻松实现命令查询职责分离模式(CQRS)

1.自定义命令类

代码如下（示例）：

class CustomCommand : IRequest<long>
    {
        public string Name { get; set; }
    }

2.自定义实现IRequestHandler的类

CustomCommandHandler 通过泛型参数来关联CustomCommand

代码如下（示例）：

class CustomCommandHandler : IRequestHandler<CustomCommand, long>
    {
        public Task<long> Handle(CustomCommand request, CancellationToken cancellationToken)
        {
            Console.WriteLine($"CustomCommand执行命令:{request.Name}");
            return Task.FromResult(100L);
        }
    }

3.通过Send来调用CustomCommand

代码如下（示例）：

 var services = new ServiceCollection();
            var assembly = typeof(Program).Assembly;
            services.AddMediatR(assembly);
            var serviceProvider = services.BuildServiceProvider();
            var mediator = serviceProvider.GetService<IMediator>();
            mediator.Send(new CustomCommand() {Name="testName" });

二、让领域事件处理更加优雅

1.自定义CustomEvent类继承INotification

代码如下（示例）：

class CustomEvent: INotification
    {
        public string Name { get; set; }
    }

2.自定义实现INotificationHandler的类

代码如下（示例）：
CusotmEventHandler1 ：

class CusotmEventHandler1 : INotificationHandler<CustomEvent>
    {
        public Task Handle(CustomEvent notification, CancellationToken cancellationToken)
        {
            Console.WriteLine($"CusotmEventHandler1 do sth:{notification.Name}");
            return Task.CompletedTask;
        }
    }

CusotmEventHandler2 ：

 class CusotmEventHandler2 : INotificationHandler<CustomEvent>
    {
        public Task Handle(CustomEvent notification, CancellationToken cancellationToken)
        {
            Console.WriteLine($"CusotmEventHandler2 do sth:{notification.Name}");
            return Task.CompletedTask;
        }
    }

3.通过Publish来调用实现了INotificationHandler的类

代码如下（示例）：

 var services = new ServiceCollection();
            var assembly = typeof(Program).Assembly;
            services.AddMediatR(assembly);
            var serviceProvider = services.BuildServiceProvider();
            var mediator = serviceProvider.GetService<IMediator>();
            await  mediator.Publish(new CustomEvent { Name = "testEventPublish" });

三、源码下载

下载

总结

Send是1:1，只能发送一个命令对象，后面的后覆盖前面的。
Publish是1：*，只要实现了INotificationHandler接口的类都能接受到消息。