Blazor Session Timeout Helper

App.razor

<body>
    <Routes @rendermode="InteractiveServer" />
    <script src="_framework/blazor.web.js"></script>
    @* Add the session helper JavaScript, used by SessionHelper.razor *@
    <script src="js/session-helper.js"></script>
</body>

MainLayout.razor

// Just add this line as the first piece of markup in the Layout file to insert it into every page that uses the layout.
<SessionHelper />

session-helper.js

window.SessionHelper = {
    TimeoutHandler: function (dotnethelper) {
        document.onmousedown = resetTimeDelay
        document.onkeypress = resetTimeDelay

        function resetTimeDelay() {
            dotnethelper.invokeMethodAsync("TimerInterval")
        }
    }
}

SessionHelper.razor

@using Microsoft.AspNetCore.Authorization
@using Microsoft.AspNetCore.Components.Authorization
@using System.Security.Claims
@using Microsoft.Graph
@using Microsoft.Graph.Models
@using BlazorApp1.Components.Layout

@inject NavigationManager NavigationManager
@inject IConfiguration Configuration
@inject IJSRuntime JSRuntime
@inject AuthenticationStateProvider AuthState

@implements IDisposable

@code {
    private System.Timers.Timer timerObj = new System.Timers.Timer();
    private Timer? SessionTimer;
    private int SessionTimeoutSeconds;

    public void Dispose()
    {
        SessionTimer?.Change(Timeout.Infinite, 0);
        SessionTimer?.Dispose();
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        await base.OnAfterRenderAsync(firstRender);

        if (firstRender)
        {
            // Identify whether the user is active or inactive using onmousemove and onkeypress in JS function.
            await JSRuntime.InvokeVoidAsync("SessionHelper.TimeoutHandler", DotNetObjectReference.Create(this));
        }
    }

    protected override async Task OnInitializedAsync()
    {
        await base.OnInitializedAsync();

        var appSettingsSection = Configuration.GetSection("AppSettings");
        SessionTimeoutSeconds = appSettingsSection?.GetValue<int>("SessionTimeout") ?? 0;

        // Check if the timeout value has been set.
        // If not, this will result in the user never being logged out due to inactivity.
        if (SessionTimeoutSeconds != 0)
        {
            //Start the timer for idle state
            SessionTimer = new Timer(HandleSessionTimeout, null, TimeSpan.FromSeconds(SessionTimeoutSeconds), Timeout.InfiniteTimeSpan);
        }
    }

    // This method is called from the JavaScript function timeOutCall in session-helper.js
    // It gets called whenever activity is detected on the page.
    [JSInvokable]
    public void TimerInterval()
    {
        // If for some reason the timer is null, return. This should never happen.
        // If it does, the session will never be refreshed.
        if (SessionTimer == null)
        {
            return;
        }
        // Reset the timer when the user is active.
        SessionTimer.Change(TimeSpan.FromSeconds(SessionTimeoutSeconds), Timeout.InfiniteTimeSpan);
    }

    // This method is called when the session timeout is reached.
    private void HandleSessionTimeout(object? state)
    {
        InvokeAsync(async () =>
        {
            // Log out when the user is inactive.
            var authState = await AuthState.GetAuthenticationStateAsync();
            var user = authState?.User;
            if (user?.Identity?.IsAuthenticated ?? false == true)
            {
                if (user?.Identity?.Name == null)
                {
                    return;
                }
                ForceSignout(user.Identity.Name);
            }
        });
    }

    private void ForceSignout(string username)
    {
            // Code to sign out the user goes here
    }
}