SignalR：带计时器的 System.ObjectDisposedException

Question

I'm playing with signalR and I want to send every 2s a little message to my clients. So I followed this tutorial , and it works good for chatting, now, I want to implement my timer. Then, I made this ( ASP.NET .NET Core 3.1 ):

public ChatHub()
{
    Debug.WriteLine("hello");
    var timer1 = new Timer();
    timer1.Elapsed += this.Timer1_Elapsed;
    timer1.Interval = 2000;
    timer1.Start();
}

private async void Timer1_Elapsed(object sender, ElapsedEventArgs e)
{
    Debug.WriteLine("tick");
    await SendMessage("user", "hello");
}

public async Task SendMessage(string user, string message)
{
    await Clients.All.SendAsync("ReceiveMessage", user, message);
}

But everytime, I get this error (in this.Clients.Add... ):

System.ObjectDisposedException: Cannot access a disposed object.

And I don't understand why, I checked stackoverflow, tried some solutions, but i'm already stuck.

Thank for your help.

---

Sample: https://github.com/Naografix/SignalRProblem

Stacktrace:

Message = "Cannot access a disposed object.\r\nObject name: 'HomeHub'."
at Microsoft.AspNetCore.SignalR.Hub.CheckDisposed()
at Microsoft.AspNetCore.SignalR.Hub.get_Clients()
at ****.HomeHub.<Timer1_Elapsed>d__1.MoveNext() in *****.Api\Hubs\HomeHub.cs:line 32

Answer 1

I can see here this:

Don't store state in a property on the hub class. Every hub method call is executed on a new hub instance.

So I decided to search how to create a service for my hub. And this is what Medium does. (Download their solution because lot of things are missing in their tutorial)

Creating a timer in my hub was a bad approach .

Solved.

Answer 2

Another way to solve your problem is create a worker to tick every 2 seconds like following:

On your ConfigureServices

services.AddHostedService<Worker>();

The worker class:

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
    while (!stoppingToken.IsCancellationRequested)
    {
        await this.hub.Clients.All.SendAsync(broadcastMethodName, "Some message...");
        await Task.Delay(2000, stoppingToken);
    }
}