這是服務端的消息

這是客戶端的消息，可以看到 無論那邊調用 的都同樣顯示了。

之前一個問題折騰了 大半天要貼出來給大家提個醒

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
 
using SignalRChat.Hubs;

namespace SignalRChat
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure
 
<CookiePolicyOptions>(options =>
            {
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });


            services.AddCors(options => options.AddPolicy("CorsPolicy",
            builder 
 
=>
            {
                builder.AllowAnyMethod().AllowAnyHeader()
                       .WithOrigins("http://localhost:12754")
                       .AllowCredentials();
            }));

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
            services.AddSignalR();
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseCookiePolicy();      
            app.UseCors("CorsPolicy");    //之前這句寫到 下面去了導致一直報跨域訪問的錯誤，順序必須在 app.UseSignalR ... 這句設置之前才行，  
            app.UseSignalR(route =>
            {
                route.MapHub<ChatHub>("/chathub");
            });
            app.UseMvc();
        }
    }
}

折騰一天終於嘗到了 signalr core了