MediatR取消发布后续消息

Question

我的Mediatr正在使用SyncContinueOnException publish strategy，有没有办法在开始传播之前运行一些验证？

示例：

_mediatr.Publish(new MyNotification());

public class MyValidationHandler :
    INotificationHandler<MyValidationHandler>
{
    Task INotificationHandler<MyValidationHandler>.Handle(MyValidationHandler notification, CancellationToken cancellationToken)
    {
        // STOP propagation if some condition is false
    }
}

public class FirstHandlers :
    INotificationHandler<MyNotification>
{
    Task INotificationHandler<MyNotification>.Handle(MyNotification notification, CancellationToken cancellationToken)
    {
        Console.WriteLine("x");
        return Task.CompletedTask;
    }
}

public class SecondHandlers :
    INotificationHandler<MyNotification>
{
    Task INotificationHandler<MyNotification>.Handle(MyNotification notification, CancellationToken cancellationToken)
    {
        Console.WriteLine("x");
        return Task.CompletedTask;
    }
}

Answer 1

更新很抱歉，最初是误读的！

包装MediatR Publish行为的一种方法是修饰IMediator实例本身，可以手动修改，也可以使用Scrutor之类的库进行修饰。您可以添加一个标记接口来标识应该通过验证逻辑传递的通知，以及任何其他事件直接传递到MediatR的通知。

public class MediatorDecorator : IMediator
{
    private readonly IMediator _mediator;

    public MediatorDecorator(IMediator mediator)
    {
        _mediator = mediator;
    }

    public Task Publish<TNotification>(TNotification notification, CancellationToken cancellationToken = default) where TNotification : INotification
    {
        if (notification is IValidatableNotification)
        {
            // Your validation behavior here
            return Task.CompletedTask; // if the validation fails, respond as you'd like ...
        }
        return _mediator.Publish(notification, cancellationToken);
    }

    // ...
}

在启动中，在MediatR注册之后，使用Scrutor的Decorate

services.AddMediatR(typeof(Startup));
services.Decorate<IMediator, MediatorDecorator>();