AspNetCore.Docs/mvc/security/cors-policy/sample/Startup.cs

using Microsoft.AspNet.Builder;
using Microsoft.AspNet.Mvc;
using Microsoft.Framework.DependencyInjection;

namespace CorsMvc
{
    public class Startup
    {

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.ConfigureCors(options =>
            {
                // Define one or more CORS policies
                options.AddPolicy("AllowSpecificOrigin",
                    builder =>
                    {
                        builder.WithOrigins("http://example.com");
                    });
            });

            services.Configure<MvcOptions>(options =>
            {
                options.Filters.Add(new CorsAuthorizationFilterFactory("AllowSpecificOrigin"));
            });
        }

        public void Configure(IApplicationBuilder app)
        {
            app.UseMvc();
        }
    }
}