generate json from mvc 5 asp.net controller

Question

My action in the controller

In the entity t_panier (means shopping cart) contains an object product that contains a list of carts(panires):

public ActionResult Indexvm()
{
    int iduser = 0;
    iduser = (int)Session["idUser"];   
    IEnumerable<t_panier> p = panSer.getAllProducts(iduser).AsEnumerable();
    return Json(p, JsonRequestBehavior.AllowGet);
}

I get this error :

Server Error in '/' Application .

Circular reference detected while serializing an object of type 'System.Data.Entity.DynamicProxies.t_product_8A57351FB72B09DE03561C95AF908FE99EBFF074229BDC8C61D7917D53F43A28'.

t_panier :

 public class t_panier
{
    public int id { get; set; }


    public int Qu { get; set; }

    public double total { get; set; }
    public Nullable<int> customer_id { get; set; }
    public Nullable<int> product_fk { get; set; }

    public virtual t_customer customer { get; set; }


    public virtual t_product product { get; set; }
}

t_product :

 public partial class t_product
{
public t_product()
    {
        this.t_order_line = new List<t_order_line>();
        this.t_review = new List<t_review>();
    }

    public int id { get; set; }
    [Required(ErrorMessage = "Name is required")]
    [StringLength(25, ErrorMessage = "Must be less than 25 characters")]
    [MaxLength(50)]
    public string title { get; set; }

    [DataType(DataType.MultilineText)]
    public string detail { get; set; }
    [DataType(DataType.Currency)]
    [Range(0, double.MaxValue)]
    public Nullable<float> price { get; set; }
    [Range(0, int.MaxValue)]
    public int quantity { get; set; }
    public Nullable<int> category_id { get; set; }
    public Nullable<int> vendor_id { get; set; }
    public virtual t_category t_category { get; set; }
    public virtual ICollection<t_order_line> t_order_line { get; set; }
    public virtual ICollection<t_review> t_review { get; set; }

    public virtual t_vendor t_vendor { get; set; }

    [Display(Name = "Image")]
    [DataType(DataType.ImageUrl)]
    public string image { get; set; }
    public virtual ICollection<t_evaluation> evaluations { get; set; }
    public virtual ICollection<t_pan> carts { get; set; }
    public virtual ICollection<t_panier> panires { get; set; }
}

Answer 1

Yes, what you are trying to serialize contains a circular reference. What that means is that 2 objects are referencing one another, so it causes an endless loop.

To fix this, you have to tell the framework to explicitly handle it. Good info here: http://johnnycode.com/2012/04/10/serializing-circular-references-with-json-net-and-entity-framework/

var jsonSerializerSettings = new JsonSerializerSettings
{
    PreserveReferencesHandling = PreserveReferencesHandling.Objects
};

GlobalConfiguration.Configuration.Formatters.Clear();
GlobalConfiguration.Configuration.Formatters.Add(new JsonNetFormatter(jsonSerializerSettings));