How Can AJAX Calls Keep ASP.NET Sessions Alive?

Prolonging ASP.NET Sessions with AJAX

Maintaining active ASP.NET sessions is vital for a smooth user experience. A robust method utilizes AJAX calls to periodically refresh the session, preventing timeouts.

Implementing an AJAX Session Heartbeat

This approach employs a jQuery AJAX call, recurring (e.g., every 5 minutes), to a dedicated HTTP handler: "SessionHeartbeat.ashx." This handler's sole purpose is session maintenance. The C# code for this handler is:

public class SessionHeartbeatHttpHandler : IHttpHandler, IRequiresSessionState
{
    public bool IsReusable { get { return false; } }

    public void ProcessRequest(HttpContext context)
    {
        context.Session["Heartbeat"] = DateTime.Now;
    }
}

The corresponding client-side JavaScript function is:

function setHeartbeat() {
    setTimeout("heartbeat()", 5*60*1000); // Every 5 minutes
}

function heartbeat() {
    $.get(
        "/SessionHeartbeat.ashx",
        null,
        function(data) {
            setHeartbeat();
        },
        "json"
    );
}

Enhancing the User Interface

For visual feedback (and continued session maintenance), we can add CSS and HTML:

function beatHeart(times) {
    var interval = setInterval(function () {
        $(".heartbeat").fadeIn(500, function () {
            $(".heartbeat").fadeOut(500);
        });
    }, 1000); // Beat every second

    // Clear interval after 'times' iterations (with 100ms buffer)
    setTimeout(function () { clearInterval(interval); }, (1000 * times) + 100);
}

/* HEARBEAT CSS */
.heartbeat {
    position: absolute;
    display: none;
    margin: 5px;
    color: red;
    right: 0;
    top: 0;
}

Advantages of AJAX Session Heartbeats

• Discreet Operation: Session maintenance is transparent to the user.
• Session Persistence: Sessions remain active as long as the browser window is open.
• Flexible Frequency: The heartbeat interval is easily adjustable.
• Improved User Experience: Ensures uninterrupted user sessions.

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