Changing the view in an ASP.NET MVC Filter

Question

I want to redirect the user to a different view if they are using a mobile browser. I've decided I'd like to do this using MVC filters by applying it to actions which I want to have a mobile view.

I believe this redirect needs to happen in OnActionExecuted, however the filterContext does not contain information on the view - it does, however in OnResultExecuted, but by this time I believe it is too late to change the view.

How can I intercept the view name and change the ViewResult?

This is what I have in the result executed and what I'd like to have work in Action Executed.

public class MobilePageFilter : ActionFilterAttribute
{
    public override void OnResultExecuted(ResultExecutedContext filterContext)
    {
        if(filterContext.Result is ViewResult)
        {
            if (isMobileSite(filterContext.HttpContext.Session[SetMobile.SESSION_USE_MOBILE]))
            {
                ViewResult viewResult = (ViewResult)filterContext.Result;

                string viewName = viewResult.ViewName;
                filterContext.Result = new ViewResult
                {
                    ViewName = "Mobile/" + viewName,
                    ViewData = viewResult.ViewData,
                    TempData = viewResult.TempData
                };
            }
        }

        base.OnResultExecuted(filterContext);
    }
}

Answer 1

I would recommend you the following blog post which explains a better alternative to achieve what you are asking for rather than using action filters.

Answer 2

This is what I ended up doing, and wrapped up into a reusable attribute and the great thing is it retains the original URL while redirecting (or applying whatever result you wish) based on your requirements:

public class AuthoriseSiteAccessAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        base.OnActionExecuting(filterContext);

        // Perform your condition, or straight result assignment here.
        // For me I had to test the existance of a cookie.
        if (yourConditionHere)
            filterContext.Result = new SiteAccessDeniedResult();
    }

}

public class SiteAccessDeniedResult : ViewResult
{
    public SiteAccessDeniedResult()
    {
        ViewName = "~/Views/SiteAccess/Login.cshtml";
    }
}

Then just add the attribute [SiteAccessAuthorise] to your controllers you wish to apply the authorisation access to (in my case) or add it to a BaseController. Make sure though the action you are redirecting to's underlying controller does not have the attribute though, or you'll be caught in an endless loop!