C# recursion limit when returning JSON

Question

I ran into an annoying issue recently. I'm going to simplify my datamodel here, but the principle is just the same. I have a class "User". In that class I have a property that is a list of objects the user owns. I also have this class "object". Because every "object" has an owner, it has a property of type "User", which links to its owner. Now, what I'm trying to do is basically this

return Json(myUser,JsonRequestBehavior.AllowGet);

When I load the page, it takes like 30 seconds and then I get the error "RecursionLimit exceeded".

I guess this is because the objects are linking to each other. Now my question is, how can I tell "Json" that it shouldn't go deeper then 1 level of objects to avoid this?

Answer 1

myUser is probably a type generated by EntityFramework.

When you return Json, the framework is going to prepare each property in essence firing off SQL command to lazy-load all the data.

Instead, you should prepare a ViewModel class with concrete properties not attached to EntityFramework and prepare that object as deep as you want it to go.

Answer 2

It might happen when your object has some properties of itself. for example.

public object Employee()
{
    string ID {get; set;}
    string Name {get; set;}
    int Age {get; set;}
    Employee Boss{get; set;} //<-- here
}

var employee = new Employee();
return Json(employee,JsonRequestBehavior.AllowGet); //The Boss property will cause "RecursionLimit exceeded".

To avoid that. you can do something like that:

var employee = new Employee();
var prepareForJson = new {
    ID = employee.ID,
    Name = employee.Name,
    Age = employee.Age,
    Boss = employee.Boss.ID
};
return Json(prepareForJson , JsonRequestBehavior.AllowGet);