Publishing a MediatR event from a MediatR command handler

[RJR-Robert-Kewei-Zhang]

Hi @jbogard,

I need to publish a MediatR event and I am wondering if I can invoke the publish method from a MetiatR command handler.

Thanks,
Robert

[jbogard]

Yes you can. Just keep in mind the notification handlers run in-process with the command handler.

[RJR-Robert-Kewei-Zhang]

Thank you Jimmy, it is really helpful
Robert

[RJR-Robert-Kewei-Zhang]

Hi Jimmy,

Below is the code sample of how I am using it, just want to be sure that we are on the same page

//MediatR, invoking send method
using MediatR;
using mediatrAPI.Commands;

namespace mediatrAPI.Controllers
{
[ApiController]
[Route("[controller]")]
public class OrderController : ControllerBase
{
private readonly IMediator _mediator;

    public OrderController(IMediator mediator)
    {
        _mediator = mediator;

    }

    [HttpPost]
    [Route("PlaceOrder")]
    public Task PostAsync([FromBody] PlaceOrderCommand order) =>
          _mediator.Send(order);
}

}

//MediatR, command handler
using MediatR;
using mediatrAPI.Events;

namespace mediatrAPI.Commands
{
public class PlaceOrderCommand : IRequest
{
public string CustomerName { get; set; }
public OrderLine[] OrderLines { get; set; }
public class OrderLine
{
public string ProductName { get; set; }
public int Quantity { get; set; }
}

    public class PlaceOrderRequestHandler : IRequestHandler<PlaceOrderCommand>
    {
        private readonly IMediator _mediator;
        public PlaceOrderRequestHandler(IMediator mediator)
        {
            _mediator = mediator;
        }
        
        
        public async Task<Unit> Handle(PlaceOrderCommand request, CancellationToken cancellationToken)
        {
            try
            {
                //Some code to save the order infomration
                //......
                //

                //Invoking the mediator publish method
                await _mediator.Publish(new OrderPlacedEvent
                {
                    productName = "Garden tools",
                    numberOfProduct = 2
                }, cancellationToken);
                return Unit.Value;
            }
            catch (Exception e)
            {
                Console.WriteLine(DateTime.Now.ToString() + ": " + e.Message);
                return Unit.Value;
            }
        }
    }
}

}

Thanks,
Robert