Angular/SignalR 错误：无法完成与服务器的协商

对我的服务器使用 SignalR，对我的客户端使用 Angular...当我运行客户端时，我收到以下错误：

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

我猜这是 CORS 的问题...我正在尝试实现一个简单的聊天应用程序。我正在使用最新版本的 SignalR：

这是 github，其中包含我正在关注的教程的代码。SignalR 聊天教程 https://github.com/Ibro/SignalRSimpleChat/blob/asp-net-core-angular/AngularAspNetCoreSignalR/Startup.cs

这是我的启动

    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<ChatHub>("/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。谢谢你！

编辑：我刚刚在 Visual Studio 中重新创建了信号器实现并且它起作用了。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();