Angular/SignalR错误：无法完成与服务器的协商

在服务器上使用SignalR，在客户端上使用Angular ...运行客户端时，出现以下错误：

zone.js:2969 OPTIONS https://localhost:27967/chat/negotiate 0 ()

Utils.js:148 Error: Failed to complete negotiation with the server: Error

Utils.js:148 Error: Failed to start the connection: Error

我猜这与CORS有关...我正在尝试实现一个简单的聊天应用程序。我正在使用SignalR的最新版本：

这是包含我要遵循的教程代码的github。 SignalR聊天教程

这是我的创业公司

    using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;

namespace signalrChat
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCors(o => o.AddPolicy("CorsPolicy", builder =>
            {
                builder
                    .AllowAnyMethod()
                    .AllowAnyHeader()
                    .WithOrigins("http://localhost:4200");
            }));

            services.AddSignalR();
        }

        // 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();
            }

            app.UseCors("CorsPolicy");

            app.UseSignalR(routes =>
            {
                routes.MapHub("/chat");
            });
        }
    }
}

这是我的客户：

    import { Component, OnInit } from '@angular/core';
import { HubConnection, HubConnectionBuilder } from '@aspnet/signalr';


@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {

  private hubConnection: HubConnection;

  nick = '';
  message = '';
  messages: string[] = [];

  ngOnInit() {
    this.nick = window.prompt('Your name:', 'John');

    this.hubCOnnection= new HubConnectionBuilder().withUrl('https://localhost:27967/chat').build();

    this.hubConnection
    .start()
    .then(() => console.log("Connection Started!"))
    .catch(err => console.log("Error while establishing a connection :( "));

    this.hubConnection.on('sendToAll', (nick: string, receiveMessage: string) => {
      const text = `${nick}: ${receiveMessage}`;
      this.messages.push(text);
    })
  }

  public sendMessage(): void {
    this.hubConnection
    .invoke('sendToAll', this.nick, this.message)
    .catch(err => console.log(err));
  }

}

我认为这可能与cors有关。谢谢！

编辑：我只是在Visual Studio中重新创建了Signalr实施，并且它起作用了。我相信我在启动时选择了错误的设置。

cOnnection= new signalR.HubConnectionBuilder()
    .configureLogging(signalR.LogLevel.Debug)
    .withUrl("http://localhost:5000/decisionHub", {
      skipNegotiation: true,
      transport: signalR.HttpTransportType.WebSockets
    })
    .build();