如何使用带有.NET Core的SignalR的Hub类的服务器端Timer？

Question

I want to apply timer from server side using SignalR in .NET Core project. I am able to start timer with custom class. Timer should be stopped on Stop button click and started on Start button click. It is just a demo I am creating like start and stop watch.

I have implemented the same using Node.js and I got no problem. In SignalR with .NET Core, it is just I am not able to get the same.

// Custom Timer class to be able to access HubCallerContext and Clients
public class CustomTimer : System.Timers.Timer
{
    public CustomTimer(double interval)
        : base(interval)
    {
    }

    public HubCallerContext callerContext { get; set; }
    public IHubCallerClients<IClient> hubCallerClients { get; set; }
}

public class ApplicationHub : Hub<IClient>
{
    public CustomTimer timer = new CustomTimer(1000);

    // This method will be called on Start button click
    public async Task StartTime()
    { 
        timer.callerContext = Context;
        timer.hubCallerClients = Clients;
        timer.Elapsed += aTimer_Elapsed;
        timer.Interval = 1000;
        timer.Enabled = true;
    }

    // This method will pass time to all connected clients
    void aTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
        timer = (CustomTimer)sender;
        HubCallerContext hcallerContext = timer.callerContext;
        IHubCallerClients<IClient> hubClients = timer.hubCallerClients;

        hubClients.Clients.All.ShowTime(DateTime.Now.Hour.ToString() +
            ":" + DateTime.Now.Minute.ToString() + ":" +
            DateTime.Now.Second.ToString());
    }

    // This should stop running timer on button click event from client
    public async Task StopTime()
    {
        timer.Elapsed -= aTimer_Elapsed;
        timer.Enabled = false;

        await Clients.All.StopTime("Timer Stopped");
    }
}

While calling StopTimer method from client, I am not getting current timer. If any one can guide me with this, I would be grateful.

Thanks
Coding means issues means fun. :)

Answer 1

Store a reference to timer in a static ConcurrentDictionary indexed by ConnectionId .

You just need to add 3 lines and change 2 lines.

public class CustomTimer : System.Timers.Timer
{
    // Add this ↓
    public static ConcurrentDictionary<string, CustomTimer> Timers = new ConcurrentDictionary<string, CustomTimer>();

    // ...
}

public class ApplicationHub : Hub<IClient>
{
    public CustomTimer timer = new CustomTimer(1000);

    // Change this ↓ to `static`, so that `timer.Elapsed -= aTimer_Elapsed;` works
    static void aTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
        // Change this ↓ to `var`
        var timer = (CustomTimer)sender;

        // ...
    }

    public async Task StartTime()
    {
        // Add this ↓
        timer = CustomTimer.Timers.GetOrAdd(Context.ConnectionId, timer);

        // ...
    }

    public async Task StopTime()
    {
        // Add this ↓
        timer = CustomTimer.Timers.GetOrAdd(Context.ConnectionId, timer);

        // ...
    }
}