ASP.NET MVC: How to create an action filter to output JSON?

Question

My second day with ASP.NET MVC and my first request for code on SO (yep, taking a short cut).

I am looking for a way to create a filter that intercepts the current o

Answer 1

I would suggest that what you really want to do is use the Model rather than arbitrary ViewData elements and override OnActionExecuted rather than OnActionExecuting. That way you simply replace the result with your JsonResult before it gets executed and thus rendered to the browser.

public class JSONAttribute : ActionFilterAttribute
{
   ...

    public override void OnActionExecuted( ActionExecutedContext filterContext)
    {
        var result = new JsonResult();
        result.Data = ((ViewResult)filterContext.Result).Model;
        filterContext.Result = result;
    }

    ...
}

[JSON]public ActionResult Index()
{
    ViewData.Model = "This is my output";
    return View();
}