How can I utilize or mimic Application OnStart in an HttpModule?

Question

We are trying to remove the global.asax from our many web applications in favor of HttpModules that are in a common code base. This works really well for many application events such as BeginRequest and PostAuthentication, but there is no Application Start event exposed in the HttpModule.

I can think of a couple of smelly ways to overcome this deficit. For example, I can probably do this:

protected virtual void BeginRequest(object sender, EventArgs e)
{
    Log.Debug("Entered BeginRequest...");
    var app = HttpContext.Current.Application;
    var hasBeenSet app["HasBeenExecuted"] == null ? false : true;

    if(!hasBeenSet)
    {
        app.Lock();
        // ... do app level code

        app.Add("HasBeenExecuted", true);
        app.Unlock();
    }

    // do regular begin request stuff ...
}

But this just doesn't smell well to me.

What is the best way to invoke some application begin logic without having a global.asax?

Answer 1

Just keep a static bool in the HttpModule:

private static bool _hasApplicationStarted = false;
private static object _locker = new object();

private void EnsureStarted()
{
    if (_hasApplicationStarted) return;

    lock (_locker)
    {
        if (_hasApplicationStarted) return;

        // perform application startup here

        _hasApplicationStarted = true;
    }
}

Then have any method that needs the application to have started just call EnsureStarted.

Answer 2

HttpModules and HttpHandlers will execute on every single request, while the Global.asax App Start event is when the application starts, thus only once.

You could make a general global.asax which will load all assemblies with a specific interface, and then drop in the dll's you want executed for that specific application. Or even register them in your web.config, and have your general global.asax read the keys, and then load and execute the code you want.

I think this is better than putting app once code in a module and checking on a state variable.