JSON.Net Deseralize json pair to Object Propery

Question

Ok I have WebApi application that is sending back name value pairs like so

{'FirstName':'SomeGuy'}

On the server the FirstName field is not just a string, it is a generic object that hold additional information about FirstName, and is not send back from the client.

Here is a outline of the classes

public abstract class Field
{
 protected object _value;
  ......More Properties/Methods
  public bool HasValue
    {
        get { return _hasValue; }
    }

    public object Value
    {
        get { return _hasValue ? _value : null; }
    }

    protected void SetValue(object value, bool clearHasValue = false)
    {
        _value = value;
        _hasValue = clearHasValue ?
            false :
            value != null;
    }
}

public class Field<T> : Field
{
  ..Constructors and methods
  public new T Value
    {
        get { return _hasValue ? (T)_value : default(T); }
        set { SetValue(value); }
    }
}

So.. In theory I may be trying to bind to a model like

 class FieldModel
    {
        public Field<string> FirstName { get; set; }
        public Field<string> LastName { get; set; }
        public Field<Decimal> Amount { get; set; }

        public FieldModel()
        {
            FirstName = new Field<string>();
            LastName = new Field<string>();
            Amount = new Field<decimal>();
        }
    }

So here is the issue.. I want FirstName in my json object to deseralize to right property. Now if I modify the json package to {'FirstName.Value':'SomeGuy'} JSON.net works out of the box, but I really not to do that. I have been tying to make my own JsonConverter but have not been able to get that to work. So, I don't think this should be very hard, but I am a bit stuck.

EDIT

So.. I did come up with a solution that works, but I have to think there is a better way.. It uses dynamics and I have to think that I am missing an easy solution.

public class FieldConverter : JsonConverter
{
    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
        {
            return null;
        }
        var internalVal = serializer.Deserialize(reader, objectType.GetGenericArguments().FirstOrDefault());
        var retVal = existingValue as dynamic;
        retVal.Value = internalVal as dynamic;
        return retVal;
    }

    public override bool CanRead
    {
        get { return true; }
    }

    public override bool CanWrite
    {
        get { return false; }
    }

    public override bool CanConvert(Type objectType)
    {
        return objectType.IsSubclassOf(typeof(Field));
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

Answer 1

You can easily do this with JSON.NET's CustomCreationConverter. Here's an example :

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public DateTime BirthDate { get; set; }
}

public class Employee : Person
{
    public string Department { get; set; }
    public string JobTitle { get; set; }
}

public class PersonConverter : CustomCreationConverter<Person>
{
    public override Person Create(Type objectType)
    {
        return new Employee();
    }
}

And the usage:

string json = @"{
  'Department': 'Furniture',
  'JobTitle': 'Carpenter',
  'FirstName': 'John',
  'LastName': 'Joinery',
  'BirthDate': '1983-02-02T00:00:00'
}";

Person person = JsonConvert.DeserializeObject<Person>(json, new PersonConverter());

Console.WriteLine(person.GetType().Name);
// Employee

Employee employee = (Employee)person;

Console.WriteLine(employee.JobTitle);
// Carpenter