项目中经常会遇到跨域问题，解决方法：
在appsettings.json 文件中添加json项
{"Logging": {"LogLevel": {"Default": "Warning"}},"AllowedHosts": "*","AppCores": "https://www.xxx0.com,https://www.xxx1.com" }
在Startup文件中进行设置
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using SignalRTestCore.SignalR;namespace SignalRTestCore
{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){services.Configure<CookiePolicyOptions>(options =>{// This lambda determines whether user consent for non-essential cookies is needed for a given request.options.CheckConsentNeeded = context => true;options.MinimumSameSitePolicy = SameSiteMode.None;}); var urls = Configuration["AppCores"].Split(',');services.AddCors(options => options.AddPolicy("AllowAll",policy => policy.WithOrigins(urls).AllowAnyMethod().AllowAnyHeader().AllowCredentials()));services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IHostingEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}else{app.UseExceptionHandler("/Error");// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.app.UseHsts();}app.UseHttpsRedirection();app.UseStaticFiles();app.UseCookiePolicy();app.UseCors("AllowAll");app.UseMvc();}}
}
在Controller类上进行跨域设置 [EnableCors("AllowAll")]
