小编pb3*_*b36的帖子

从浏览器访问时出现此错误

从源“https://example.com”访问“https://api.example.com/users/authenticate”处的 XMLHttpRequest 已被 CORS 策略阻止：对预检请求的响应未通过访问控制检查：否请求的资源上存在“Access-Control-Allow-Origin”标头

启动.cs

using System;
using System.Text;
using BackendRest.Helper;
using BackendRest.Models;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpOverrides;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.IdentityModel.Tokens;

namespace BackendRest
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        readonly string CorsApi = "_CorsApi";
        public IConfiguration Configuration { get; }
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCors(options =>
            {
                options.AddPolicy(CorsApi,
                    builder =>
                    {
                        builder
                        .AllowAnyOrigin()
                        .AllowAnyMethod()
                        .AllowAnyHeader();
                    });
            });
            services.AddControllers().AddNewtonsoftJson();
            services.AddDbContext<backenddbContext>(x => …