Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.OpenApi.Models;
using News_site.Data;
using News_site.Services;
using Sieve.Models;
using Sieve.Services;

namespace News_site
{
	public class Startup
	{
		readonly string MyAllowSpecificOrigins = "_myAllowSpecificOrigins";

		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)
		{
			services.AddCors(options =>
			{
				options.AddPolicy(name: MyAllowSpecificOrigins,
				policy =>
				{
					policy.AllowAnyOrigin();
					policy.AllowAnyMethod();
					policy.AllowAnyHeader();
				});
			});

			services.Configure<SieveOptions>(Configuration.GetSection("Sieve"));

			services.AddSingleton<ICronbot, Cronbot>();
			services.AddHostedService<CronjobService>();
			services.AddScoped<SieveProcessor>();
			services.AddDbContext<DataContext>();

			services.AddControllers().AddNewtonsoftJson(options => options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore);

			ConfigureSwagger(services);
		}

		private static void ConfigureSwagger(IServiceCollection services)
		{
			services.AddSwaggerGen(c =>
			{
				c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
			});
		}

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

			app.UseSwaggerUI(c =>
			{
				c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
			});

			if (env.IsDevelopment())
			{
				app.UseDeveloperExceptionPage();
			}

			app.UseHttpsRedirection();

			app.UseRouting();

			app.UseCors(MyAllowSpecificOrigins);

			app.UseAuthorization();

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