Why self reference loop cannot be deserialized? [It can be deserialized]

Question

Looks like no C# JSON serialization framework can deserialize self reference loop.

But why?

Let's imagine that we have this class structure:

public class Person
{
    public string Name { get; set; };
    public City City { get; set; }
}

public class City
{
   public string Name { get; set; }
   public List<Person> Persons { get; set; }
}

and in serialization/deserialization settings we say that if objects are the same put $ref instead of serializing object again

and serialized person will look like this

{
"$id":"1",
"Name":"John",
"City":{
    "$id":"2",
    "Name":"London",
    "Persons":[
        {
           "$ref":"1"
        }
     ]

and on deserialization you are simply creating person with no City then creating City with person and initialize person property with created City

    var person = new Person();
    var city = new City();
    city.Persons = new List<Person>{ person };
    person.City = city;

One explanation I can find was that if you have no empty constructors, you need to create parameters first.

But even if you have one, all serializing frameworks that I can find cannot deserialize it properly.

EDIT: IT CAN BE DESERIALIZED.

I thought that structure in the example is according to my real class structure, my real structure was not deserializing properly, so I didn't try to really serialize/deserialize structure from the example. Then, when I tried it was deserialized fine, so I checked my real structure and the reason why it was not deserializing properly is that I missed setter on property.

Moho · Accepted Answer · 2022-01-23 23:59:08Z

1

You didn’t show any actual attempts to serialize/deserialize so I don’t know what you’ve tried, but it took me 30s to find out how to do it with System.Text.Json so I suggest you give that a try. It involves configuring the ReferenceHandler option in JsonSerializerOptions

        JsonSerializerOptions options = new()
        {
            ReferenceHandler = ReferenceHandler.Preserve,
            WriteIndented = true
        };

Microsoft page devoted to this topic

answered Jan 23, 2022 at 23:59

Moho

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1 Comment

Kliment Nechaev Over a year ago

My fault. It's working fine. The structure in the example is not real, I made it according to the real structure, but apparently I'm missing something. I will check what's missing and edit the question.

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