Hi Marcio.

I have almost exact code, here it is :

public class OffersSurfaceController : SurfaceController
{
    public ActionResult GetFilteredOffers(int ? offersTypeId)
    {
        IEnumerable<IPublishedContent> allOffers = Umbraco.Content(1362).Children();
        return Json(allOffers.Where(x => x.GetPropertyValue<int>("offersItemCategory") == 1353),  JsonRequestBehavior.AllowGet);
    }
}

And i changed it 100 times, tried everything but i always get same error:

A circular reference was detected while serializing an object of type 'Umbraco.Web.Models.DynamicPublishedContent'.

The error flashes when something comes from database, when it is empty it works and logs empty array in console(I am using ajax request).

I have seen the example u linked mate but id didn't worked for me. After you said that u had already used this example and it works I copied whole example and try to make it work. At last i got perfectly working controller with ajax request which returns json response. Here is code if anyone will need it in future :

public class OffersSurfaceController : SurfaceController
{
    public ActionResult GetFilteredOffers(int ? offersTypeId, int ? offersCategoryId)
    {
        IEnumerable<IPublishedContent> allOffers = Umbraco.Content(1362).Children();
        if (offersCategoryId != 0 && offersCategoryId != null)
        {
            allOffers = allOffers.Where(x => x.GetPropertyValue<int>("offersItemCategory") == offersCategoryId);
        }

        if (offersTypeId != 0 && offersTypeId != null)
        {
            allOffers = allOffers.Where(x => x.GetPropertyValue<int>("offersItemType") == offersTypeId);
        }

        return Json(allOffers.Select(l => new { text = l.GetPropertyValue("offersItemTitle") }),  JsonRequestBehavior.AllowGet);
    }
}

Notice allOffers.Select(l => new { text = l.GetPropertyValue("offersItemTitle") }) makes code working, ToList(), ToArray() gives error which i mentioned above.

Thanks to Marcio.

I am looking forward for it, thanks in advance :)