Quick Implementation of Cross-Origin Access in ASP.NET Core 3.1

        readonly string ganweiCosr = "AllowSpecificOrigins";

Startup.ConfigureServices 中，添加服务

#if CORS
            services.AddCors(options =>
            {
                options.AddPolicy(ganweiCosr,
                builder => builder.AllowAnyHeader()
                .AllowAnyMethod()
                .AllowAnyOrigin());
            });
#endif

中间件中，有两处地方要修改

            app.UseRouting();

#if CORS
            app.UseCors(ganweiCosr);
#endif

            app.UseAuthentication();
            app.UseAuthorization();


            app.UseEndpoints(endpoints =>
            {
#if CORS
                endpoints.MapControllers().RequireCors(ganweiCosr);
#else
                endpoints.MapControllers();
#endif
            });

通过上面代码，即可实现全局跨域。