How to deserialize Newtonsoft Json.NET references to separate, individual instances

Question

I have a piece of JSON that looks like this:

[
  {
    \"$id\": \"1\",
    \"Name\": \"James\",
    \"BirthDate\": \"1983-03-08T00:00Z\",
    \"LastModified\         


        

Answer 1

You could use a custom reference resolver. For example, assuming Name is the "primary key" for your objects, this should work. Of course, you may want to make it more generic.

public class PersonReferenceResolver : IReferenceResolver
{
    private readonly IDictionary _objects = 
        new Dictionary();

    public object ResolveReference(object context, string reference)
    {
        Person p;
        if (_objects.TryGetValue(reference, out p))
        {
            //This is the "clever" bit. Instead of returning the found object
            //we just return a copy of it.
            //May be better to clone your class here...
            return new Person
            {
                Name = p.Name,
                BirthDate = p.BirthDate,
                LastModified = p.LastModified
            };
        }

        return null;
    }

    public string GetReference(object context, object value)
    {
        Person p = (Person)value;
        _objects[p.Name] = p;

        return p.Name;
    }

    public bool IsReferenced(object context, object value)
    {
        Person p = (Person)value;

        return _objects.ContainsKey(p.Name);
    }

    public void AddReference(object context, string reference, object value)
    {
        _objects[reference] = (Person)value;
    }
}

Now you deserialise like this:

var jsonSerializerSettings = new JsonSerializerSettings()
{
    ReferenceResolver = new PersonReferenceResolver()
};

var deserializedPersons = JsonConvert.DeserializeObject>(
    json, jsonSerializerSettings);

---

Edit: I was bored so I made a generic version:

public class GenericResolver : IReferenceResolver
    where TEntity : ICloneable, new()
{
    private readonly IDictionary _objects = new Dictionary();
    private readonly Func _keyReader;

    public GenericResolver(Func keyReader)
    {
        _keyReader = keyReader;
    }

    public object ResolveReference(object context, string reference)
    {
        TEntity o;
        if (_objects.TryGetValue(reference, out o))
        {
            return o.Clone();
        }

        return null;
    }

    public string GetReference(object context, object value)
    {
        var o = (TEntity)value;
        var key = _keyReader(o);
        _objects[key] = o;

        return key;
    }

    public bool IsReferenced(object context, object value)
    {
        var o = (TEntity)value;
        return _objects.ContainsKey(_keyReader(o));
    }

    public void AddReference(object context, string reference, object value)
    {
        if(value is TEntity)
            _objects[reference] = (TEntity)value;
    }
}

With slightly new usage:

var jsonSerializerSettings = new JsonSerializerSettings()
{
    //Now we need to specify the type and how to get the object's key
    ReferenceResolver = new GenericResolver(p => p.Name)
};

var deserializedPersons = JsonConvert.DeserializeObject>(
    json, jsonSerializerSettings);