为什么ASP.NET Core 2 Web API会出现404错误？

Question

直到将新控制器添加到ASP.NET Core（v2.1）Web API之前，都没有问题。现在，我所有的控制器都出现404错误。最后添加的控制器是UsersController。我不确定是否更改了其他内容。

UsersController.cs

using System.Threading.Tasks;
using DatingApp.API.Data;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;

namespace DatingApp.API.Controllers
{
    [Authorize]
    [Route("api/[controller]")]
    [ApiController]
    public class UsersController : ControllerBase
    {
        private readonly IDatingRepository _repo;
        public UsersController(IDatingRepository repo)
        {
            _repo = repo;
        }

        [HttpGet]
        public async Task<IActionResult> GetUsers()
        {
            var users = await _repo.GetUsers();

            return Ok(users);
        }

        [HttpGet("{id}")]
        public async Task<IActionResult> GetUser(int id)
        {
            var user = await _repo.GetUser(id);

            return Ok(user);
        }
    }
}

launchSettings.json

{
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "api/values",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "DatingApp.API": {
      "commandName": "Project",
      "launchBrowser": false,
      "launchUrl": "api/values",
      "applicationUrl": "http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

Startup.cs

public void Configure(IApplicationBuilder app, IHostingEnvironment env, Seed seeder)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler(builder => {
                    builder.Run(async context => {
                        context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
                        var error = context.Features.Get<IExceptionHandlerFeature>();
                        if(error != null)
                        {
                            context.Response.AddApplicationError(error.Error.Message);
                            await context.Response.WriteAsync(error.Error.Message);
                        }
                    });
            //    app.UseHsts();
            });

            // app.UseHttpsRedirection();
            // seeder.SeedUsers();
            app.UseCors(x => x.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader());
            app.UseAuthentication();
            app.UseMvc(); 
            }
        }

到目前为止，我一直尝试重新启动Kestrel Web服务器。对我没用。