Creating Command Handlers

Create the command handler class file and write three classes TestCommand, TestCommandRequest and RequestValidator like so;

#!csharp

namespace Web_API_Spike.Commands
{
    [Validator(typeof(RequestValidator))]
    public class TestCommandRequest : IRequest<string>
    {
        public string Message;

        public class RequestValidator : AbstractValidator<TestCommandRequest>
        {
            public RequestValidator()
            {
                RuleFor(r => r.Message).NotEmpty().WithMessage("message cannot be empty");
            }
        }
    }

    public class TestCommand: IRequestHandler<TestCommandRequest, string>
    {
        public string Handle(TestCommandRequest message)
        {
            return message.Message;
        }
    }
}

In the controller, specify a POST route like this;

#!csharp

[HttpPost]
[Route("echo")]
public IHttpActionResult Echo(TestCommandRequest request)
{
    var echoMessage = _mediator.Send(request);
    return Ok(new { Message = echoMessage });
}

Web API will run your validation against the request object before this route is hit against the rule specified and return before the route is hit. If the request validates, then it will call the Echo method. The request is then dispatched synchronously with the mediator which will cause the command handler to be called. There is also a SendAsync() method on the mediator for longer running requests.

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Web API Spike / Creating Command Handlers

Creating Command Handlers