How to call a function *only once* in ASP.NET MVC page cycle

Question

I have an ASP.NET MVC web app and have a function that I need to call when the page loads only once. Right now I have the function being called from a base controller OnActionExecuted.

The issue I'm having is that this function is called multiple times - once for the page, and then multiple times for different ajax calls that I have on the page. I've tried putting the function on Controller Initialize but this is also called for each ajax call to a controller action. So is there some function in the ASP.NET MVC page cycle that only gets called when a page is requested (GET) and not for all of the ajax calls (POST)? The only thing I can think of is putting all of the ajax calls in separate controllers that don't inherit from the base controller but there must be a nicer solution.

Answer 1

It came to me right after posting the question...

protected override void Initialize(System.Web.Routing.RequestContext requestContext)
{
    base.Initialize(requestContext);
    if (Request.HttpMethod == "GET")
    {
        LoadConfiguration();
    } 
}

Answer 2

Depending on how you're doing your AjaxRequests you could use something like the following:

public ActionResult Index()
{
    if (!Request.IsAjaxRequest())
    {
        LoadConfiguration();
    }

    // Rest of Action method (snip)...
}

This works if, for instance, you're performing Ajax with the jQuery JavaScript library which sends a special token to the server to indicate that it's an Ajax call (I'm sure other libraries do this). This might be better just in case someone changes the JavaScript code to perform GET Ajax requests.

---

One thing you mentioned does intrigue me though "The issue I'm having is that this function is called multiple times" - actually 'technically' this is not true. It IS only getting called once....per request, all those Ajax calls are treated as separate requests by the server, as if the user is requesting a page via the web browser. It sounds like what you really need is a way to differentiate between web page HTTP Requests, and Ajax HTTP Requests, hence the above solution.

Answer 3

You can either do this work in the application scope (on start, in global.asax or other similar approaches), or store a configuration object in the session (or a flag to identify it has already been done, if there is nothing to store).