Handling Circular References ASP.NET MVC Json Serialization

I love the Entity Framework CodeFirst stuff, combined with scaffolding, it makes development go so fast. Fast that is until you drop an API into the mix and want that to serve Json.

Here’s my EF Model. Lots of lovely navigation properties allowing me to get from any entity to any other one. Handy-dandy in .NET land…

But no-bueno when serializing using the out of the box Json serializer…

[HttpGet]
public JsonResult Get(int id)
{
    return Json(itemcategoryRepository.Find(id),
        JsonRequestBehavior.AllowGet);
}

Now, this sucks because how awesomely elegant is that code? What you get is an error like this:

A circular reference was detected while serializing an object of type ‘System.Data.Entity.DynamicProxies.ItemCategory_A79…’.

Json Serialization Options

There are a few ways to go here – you could use ViewModels everywhere and sloppy-copy properties across as needed. Even with Automapper to take the drugery out of this, it rubs me the wrong way – what’s the point of using EF if I still have to have a separate set of Poco ViewModels?

Another option is to add a .ToJson method to the EF classes, and emit strings. Lots of control, but… meh.

Using Json.net comes up a lot, but it’s also labor intensive.

What I ended up doing is using Linq to project the EF object graph into an anonymous object graph. Here’s an example that serializes two levels of objects (a list of ItemCategories, each of which can contain a list of Items – see the object model above)

[HttpGet]
public JsonResult List()
{
    var data = itemcategoryRepository
        .AllIncluding(itemcategory => itemcategory.Items);
    //Project into anonymous objects because Serializers
    //can't handle circular refs in the EF magic
    var collection = data.Select(x => new
    {
        id = x.Id,
        name = x.Name,
        items = x.Items.Select(item => new
        {
            id=item.Id,
            name = item.Name
        })
    });
    return Json(collection,
        JsonRequestBehavior.AllowGet);
}

I like this solution because I have control of the Json in the controller, rather than forcing an object to always serialize the same way in all cases (sometimes I want the Item to serialize it’s Entries, but only when I’m getting a single Item).