Slim Controller + MediatR

WeatherForecastController.cs

using MediatR;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using System.ComponentModel.DataAnnotations;

namespace SlimController.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class WeatherForecastController : ControllerBase
    {
        private readonly ILogger<WeatherForecastController> _logger;
        private readonly IMediator _mediator;

        public WeatherForecastController(ILogger<WeatherForecastController> logger, IMediator mediator)
        {
            _logger = logger;
            _mediator = mediator;
        }

        [HttpGet(Name = "GetWeatherForecast")]
        public async Task<IActionResult> Get([FromQuery] GetFutureWeatherRequest request)
        {
            return (await _mediator.Send(request)).Result;
        }
    }

    public class GetFutureWeatherRequest : IRequest<GetFutureWeatherResponse>
    {
        [Range(1, 10)]
        public int DaysToForecast { get; set; }
    }

    public class GetFutureWeatherResponse
    {
        public GetFutureWeatherResponse(IActionResult result)
        {
            _result = result;
        }
        private IActionResult _result;
        public IActionResult Result
        {
            get { return _result; }
        }

        public class GetFutureWeatherRequestHandler : IRequestHandler<GetFutureWeatherRequest, GetFutureWeatherResponse>
        {
            private static readonly string[] Summaries = new[]
            {
                "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
            };

            public Task<GetFutureWeatherResponse> Handle(GetFutureWeatherRequest request, CancellationToken cancellationToken)
            {
                var forecast = Enumerable.Range(1, request.DaysToForecast).Select(index => new WeatherForecast
                {
                    Date = DateTime.Now.AddDays(index),
                    TemperatureC = Random.Shared.Next(-20, 55),
                    Summary = Summaries[Random.Shared.Next(Summaries.Length)]
                })
                .ToArray();

                var response = new GetFutureWeatherResponse(new OkObjectResult(forecast));
                return Task.FromResult(response);
            }
        }
    }
}