Question

I’ve just started a new project in ASP.net 4.0 with MVC 2.

What I need to be able to do is have a custom hook at the start and end of each action of the controller.

e.g.

public void Index() {  
    *** call to the start custom hook to externalfile.cs (is empty so does nothing)

    ViewData["welcomeMessage"] = "Hello World";

    *** call to the end custom hook to externalfile.cs (changes "Hello World!" to "Hi World")

    return View();
}

The View then see welcomeMessage as “Hi World” after being changed in the custom hook.

The custom hook would need to be in an external file and not change the “core” compiled code. This causes a problem as with my limited knowledge ASP.net MVC has to be compiled.

Does anyone have any advice on how this can be achieved?

Thanks

Answer 1

You create your own class based on the ActionFilterAttribute. It has the following hooks.

1. OnActionExecuted
2. OnActionExecuting
3. OnResultExecuted
4. OnResultExecuting

For example,

public class MyFilterAttribute : ActionFilterAttribute
{
    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        var controller = filterContext.Controller;

        controller.ViewData["welcomeMessage"] = "Hi World!";
        controller.TempData["Access_My_TempData"] = "Some Value";

        base.OnActionExecuted(filterContext);
    }
}

You can also check what type of [Action] the Action method is performing.

if ((filterContext.Result is RedirectResult) || (filterContext.Result is RedirectToRouteResult))
{
    // do something only if we are redirecting to a different action
}
else if (filterContext.Result is ViewResult)
{
    // this is just a normal View action
}

Oh I forgot to show how to use the attribute.
You just decorate on top of your Action Method.

[MyFilterAttribute]
public ActionResult MyActionMethod()
{
    return View();
}