没有 'Access-Control-Allow-Origin' header 错误，即使它已在 SignalR 服务器上配置

Question

我正在尝试连接到我本地机器上的 SignalR 应用程序，运行在与 Angular 5 应用程序不同的端口上。我收到以下错误。我做错了什么？

加载失败http://localhost:52527/chatHub: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:4200'因此不允许访问。

以下是 angular 代码。

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

@Component({
  selector: 'app-register',
  templateUrl: './register.component.html',
  styleUrls: ['./register.component.css']
})
export class RegisterComponent implements OnInit {
  private hubConnection: HubConnection;

  constructor(private http: Http) {
  }

    ngOnInit() {

          this.hubConnection = new HubConnection('http://localhost:52527/chatHub');

          console.log(this.hubConnection);
          this.hubConnection
            .start()
            .then(function (){ 
               console.log('Connection started!');
            })
            .catch(function(err) {
              console.log(err);
            } );
          }

}

服务器代码如下

[assembly: OwinStartup(typeof(SignalRChat.Startup))]
namespace SignalRChat
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            // Any connection or hub wire up and configuration should go here

            app.Map("/signalr", map =>
            {
                map.UseCors(CorsOptions.AllowAll);
                var hubConfiguration = new HubConfiguration {};
                map.RunSignalR(hubConfiguration);
            });
        }
    }
}

Answer 1

向 Web.Config 添加了以下几行并解决了问题。

<system.webServer>
    <httpProtocol>
        <customHeaders>
            <add name="Access-Control-Allow-Origin" value="*" />
            <add name="Access-Control-Allow-Headers" value="*" />
        <add name="Access-Control-Allow-Methods" value="*" />
        </customHeaders>
    </httpProtocol>
</system.webServer>

没有 'Access-Control-Allow-Origin' header 错误，即使它已在 SignalR 服务器上配置

No 'Access-Control-Allow-Origin' header error, even though it has been configured on SignalR server

signalr

angular5