How to hook up SignalR with an Angular 7 application

Question

I simply cannot figure out how to make a signalr connection from Angular.

Using the following tutorial at https://docs.microsoft.com/en-us/aspnet/signalr/overview/gettin

Answer 1

• Angular app

Install signalR package

npm i @aspnet/signalr --save

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

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

  private hubConnection: HubConnection;

  public ngOnInit() {
    this.hubConnection = new signalR.HubConnectionBuilder()
      .withUrl("http://localhost:50930/pushNotification").build();

    this.hubConnection.start().then(() => {
      console.log("connection started");
    }).catch(err => console.log(err));

    this.hubConnection.onclose(() => {
      debugger;
      setTimeout(() => {
        debugger;
        this.hubConnection.start().then(() => {
          debugger;
          console.log("connection started");
        }).catch(err => console.log(err));
      }, 5000);
    });

    this.hubConnection.on("clientMethodName", (data) => {
      debugger;
      console.log(data);
    });

    this.hubConnection.on("WelcomeMethodName", (data) => {
      debugger;
      console.log(data);
      this.hubConnection.invoke("GetDataFromClient", "user id", data).catch(err => console.log(err));
    });
  }

  public stopConnection() {
    this.hubConnection.start().then(() => {
      console.log("stopped");
    }).catch(err => console.log(err));
  }
}

• Web API with netcoreapp2.2

  Install Microsoft.AspNetCore.SignalR

Startup.cs

Client is running on port 4200 ("http://localhost:4200").

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace SignalRWebApp
{
    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.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

            services.AddCors(option =>
            {
                option.AddPolicy("CorsPolicy", builder =>
                         builder.WithOrigins("http://localhost:4200")
                        .AllowAnyMethod()
                        .AllowAnyHeader()
                        .AllowCredentials());
            });
            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("/pushNotification");
            });

            app.UseHttpsRedirection();
            app.UseMvc();
        }
    }
}

SignalHub.cs

using Microsoft.AspNetCore.SignalR;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace SignalRWebApp
{
    public class SignalHub : Hub
    {
        public void GetDataFromClient(string userId, string connectionId)
        {
            Clients.Client(connectionId).SendAsync("clientMethodName", $"Updated userid {userId}");
        }

        public override Task OnConnectedAsync()
        {
            var connectionId = Context.ConnectionId;
            Clients.Client(connectionId).SendAsync("WelcomeMethodName", connectionId);
            return base.OnConnectedAsync();
        }

        public override Task OnDisconnectedAsync(Exception exception)
        {
            var connectionId = Context.ConnectionId;
            return base.OnDisconnectedAsync(exception);
        }
    }
}

Now send signalR message like the below example

[Route("api/[controller]")]
    [ApiController]
    [EnableCors("CorsPolicy")]
    public class ValuesController : ControllerBase
    {
        private IHubContext _hub;
        public ValuesController(IHubContext hub)
        {
            _hub = hub;
        }

        // GET api/values
        [HttpGet]
        public ActionResult> Get()
        {
            _hub.Clients.All.SendAsync("clientMethodName", "get all called");
            return new string[] { "value1", "value2" };
        }

        // GET api/values/5
        [HttpGet("{connectionId}")]
        public ActionResult Get(string connectionId)
        {
            _hub.Clients.Client(connectionId).SendAsync("clientMethodName", "get called");
            return "value";
        }
    }
}

Github