How to tell when a user leaves the site with Blazor Server Side

Blazor server side is built on signalr, so I would assume that it knows when a user leaves the website (closes the connection). Is there any event raised that I can use to log this? Or any other way really!

I think this service can help you...

public class CircuitHandlerService : CircuitHandler 
    {
        public ConcurrentDictionary<string, Circuit> Circuits { get; set; }
        public event EventHandler CircuitsChanged;

        protected virtual void OnCircuitsChanged()
        => CircuitsChanged?.Invoke(this, EventArgs.Empty);

        public CircuitHandlerService()
        {
            Circuits = new ConcurrentDictionary<string, Circuit>();
        }

        public override Task OnCircuitOpenedAsync(Circuit circuit, CancellationToken cancellationToken)
        {
            Circuits[circuit.Id] = circuit;
            OnCircuitsChanged();
            return base.OnCircuitOpenedAsync(circuit, cancellationToken);
        }

        public override Task OnCircuitClosedAsync(Circuit circuit, CancellationToken cancellationToken)
        {
            Console.WriteLine("OnCircuitClosedAsync");
            Circuit circuitRemoved;
            Circuits.TryRemove(circuit.Id, out circuitRemoved);
            OnCircuitsChanged();
            return base.OnCircuitClosedAsync(circuit, cancellationToken);
        }

        public override Task OnConnectionDownAsync(Circuit circuit, CancellationToken cancellationToken)
        {
            Console.WriteLine("OnConnectionDownAsync");
            return base.OnConnectionDownAsync(circuit, cancellationToken);
        }

        public override Task OnConnectionUpAsync(Circuit circuit, CancellationToken cancellationToken)
        {
            return base.OnConnectionUpAsync(circuit, cancellationToken);
        }
               
    }

Testing

Index.razor

@page "/"

@using Microsoft.AspNetCore.Components.Server.Circuits
@using BlazorCircuitHandler.Services

@inject CircuitHandler circuitHandler
@implements IDisposable



<h1>Hello, world!</h1>

Welcome to your new app.

<p>
    Number of Circuits: @((circuitHandler as <BlazorCircuitHandler is a name space in my app>.Services.CircuitHandlerService).Circuits.Count)
    <ul>
        @foreach (var circuit in (circuitHandler as BlazorCircuitHandler.Services.CircuitHandlerService).Circuits)
        {
            <li>@circuit.Key</li>
        }
    </ul>
</p>

@code {

    protected override void OnInitialized()
    {
        (circuitHandler as CircuitHandlerService).CircuitsChanged += HandleCircuitsChanged;
        
    }

    public void Dispose()
    {
        
        (circuitHandler as CircuitHandlerService).CircuitsChanged -= HandleCircuitsChanged;
       
    }

    public void HandleCircuitsChanged(object sender, EventArgs args)
    {
        // notify the UI that the state has changed
          InvokeAsync(() => StateHasChanged());
    }
}

Startup.cs

public void ConfigureServices(IServiceCollection services)
        {
            services.AddRazorPages();
            services.AddServerSideBlazor();

            services.AddSingleton<CircuitHandler>(new CircuitHandlerService());
        }

Hope this helps...