Intercept JsonResult and wrap it (as string) - asp.net-mvc

Question

I have a action that return JsonResult.
I want to intercept the JsonResult return and wrap it with string.
Something like:
public class JsonProxyAttribute : FilterAttribute
{
void OnActionExecuting(ExceptionContext filterContext)
{
var res = filterContext.Result as string;
if (res != null)
{
filterContext.Result = "func("+filterContext.Result+")";
}
}
}
So the ajax call will get this:
func({"MyContent":"content"})
instead of this:
{"MyContent":"content"}

Answer 1

What you need is to create a new ActionResult that will extend JsonResult and represent JSONP
public class JsonpResult : JsonResult
{
public override void ExecuteResult(ControllerContext context)
{
HttpResponseBase response = context.HttpContext.Response;
response.ContentType = ContentType ?? "application/x-javascript";
response.ContentEncoding = ContentEncoding ?? System.Text.Encoding.UTF8;
if (Data != null)
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
string ser = serializer.Serialize(Data);
response.Write("func(" + ser + ");");
}
}
}
Now if you want to intercept regular JSON results, your ActionFilter would look like this.
public class JsonProxyAttribute : FilterAttribute
{
void OnActionExecuting(ExceptionContext filterContext)
{
var res = filterContext.Result as JsonResult;
if (res != null)
{
filterContext.Result = new JsonpResult
{
ContentEncoding = res.ContentEncoding,
ContentType = res.ContentType,
Data = res.Data,
JsonRequestBehavior = res.JsonRequestBehavior
};
}
}
}
Or you can use JSONP directly in your controllers
public ActionResult Jsonp()
{
var model = new List<string> { "one", "two" };
return new JsonpResult
{
Data = model,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}