仍然收到错误消息，已被CORS政策阻止

我在Angular 8中有一个asp.net core 3应用程序。因此在Angular中我有以下方法：

 getValues() {
    this.http.get('https://localhost:44323/api/Values/').subscribe(response => {
      this.values = response;
    }, error => {
      console.log(error);
    });
  }

我的cs文件看起来像这样：

 public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {

            string connectionString = Configuration["ConnectionStrings:DefaultConnection"];
            services.AddDbContext<DataContext>(options =>
            options.UseSqlServer(connectionString));

            services.AddCors();

            services.AddControllers();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseCors();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });

            app.UseCors(x => x.WithOrigins().AllowAnyMethod().AllowAnyHeader());

        }
    }

所以我正在做UseCors的事情。但我仍然收到此错误：

Access to XMLHttpRequest at 'https://localhost:44323/api/Values/' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

当然我用谷歌搜索了这个错误。这就是为什么我使用UseCors的原因。但这是他们所建议的。但我仍然会收到此错误。

所以我被困住了。如果有人可以告诉我我做错了，那将很好。

谢谢

我现在有这样的东西：

[EnableCors("AllowOrigin")]
    [Route("api/[controller]")]
    [ApiController]
    public class ValuesController : ControllerBase
    {

        private protected DataContext _dataContext;
        public ValuesController( DataContext dataContext)
        {
            this._dataContext = dataContext;
        }
        // GET api/values
        [HttpGet]
        [EnableCors("AllowOrigin")]
        public async Task <IActionResult> GetValues()
        {
            var values = await _dataContext.Values.ToListAsync();

            return Ok(values);

        }

        // GET api/values/5
        [HttpGet("{id}")]
        public async Task <IActionResult> GetValue(int id)
        {
            var value = await _dataContext.Values.FirstOrDefaultAsync(x => x.Id == id);

            return Ok(value);
        }

        // POST api/values
        [HttpPost]
        public void Post([FromBody] string value)
        {
        }

        // PUT api/values/5
        [HttpPut("{id}")]
        public void Put(int id, [FromBody] string value)
        {
        }

        // DELETE api/values/5
        [HttpDelete("{id}")]
        public void Delete(int id)
        {
        }
    }

和这个：

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {

            string connectionString = Configuration["ConnectionStrings:DefaultConnection"];
            services.AddDbContext<DataContext>(options =>
            options.UseSqlServer(connectionString));

            services.AddCors();
            //services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

            services.AddControllers();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            //app.UseCors();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });

            app.UseCors(x => x.WithOrigins("https://localhost:44323").AllowAnyHeader().AllowAnyMethod().AllowCredentials());

        }
    }

但是然后我会得到这个错误：

An unhandled exception occurred while processing the request.
InvalidOperationException: Endpoint DatingApp.API.Controllers.ValuesController.GetValues (DatingApp.API) contains CORS metadata, but a middleware was not found that supports CORS.
Configure your application startup by adding app.UseCors() inside the call to Configure(..) in the application startup code.
Microsoft.AspNetCore.Routing.EndpointMiddleware.ThrowMissingCorsMiddlewareException(Endpoint endpoint)