Simple .NET keep alive handler to prevent timeout

What is it all about?

This post shows you how to create a keep alive for a .NET website so people can stay logged in whilst the page is open, instead of it timing out after 20 minutes.

The basic premise to this is:

• Create a handler which responds with an OK message and doesn't allow caching.
• Add some javascript to the page to call the handler every 10 minutes.
• The call to the server side handler keeps the session alive.

Here's how to do it:

1. Create a folder in your web project called Handlers, if you don't have one already.
2. Add a class called KeepAlive.cs
3. Add the following code to the KeepAlive class

using System.Web;
using System.Web.SessionState;
namespace CodeShare.Web.Handlers
{
    public class KeepAlive : IHttpHandler, IRequiresSessionState
    {
        public void ProcessRequest(HttpContext context)
        {
            context.Response.AddHeader("Cache-Control", "no-cache");
            context.Response.AddHeader("Pragma", "no-cache");
            context.Response.ContentType = "text/plain";
            context.Response.Write("OK");
        }
        public bool IsReusable { get { return false; } }
    }
}

4. In the web.config file at the root of the site, register this handler. 

<configuration>
    <system.webServer> 
        <handlers>
            <remove name="KeepAlive" />
                <add name="KeepAlive" verb="GET" path="<mark>keep-alive.ashx</mark>" type="CodeShare.Web.Handlers.KeepAlive " />
        </handlers>
    </system.webServer>
</configuration>

5. Create a javascript file in your scripts or js folder called keepAlive.js 

//calls the keep alive handler every 600,000 miliseconds, which is 10 minutes
var keepAlive = {
    refresh: function () {
        $.get('<mark>/keep-alive.ashx</mark>');
        setTimeout(keepAlive.refresh, 6000000);
    }
}; $(document).ready(keepAlive.refresh());

6. Reference the keepAlive.js file in your page, like this:

<script src="/scripts/keepAlive.js"></script>

Or you could inlcude it in your script bundle, see my post about how to use bundling and minification in MVC and Umbraco.

If you are using this with Umbraco, you will need to add the address of the keep alive handler to the umbracoReservedPaths key in the appSettings.

<add key="umbracoReservedPaths" value="~/umbraco,~/install/,~/bundles/,<mark>~/keep-alive.ashx</mark>" />

That's it, the javascript will keep calling the handler every 10 minutes or however long you set, and that will keep the session alive.