Deserialize an ExpandoObject into Object

Question

I have an object that will be used with multiple clients. The object has a set of fixed properties that are common among all clients. Here is an example of what an object may look like:

public class Applicant
{
    public string ApplicantId { get; set; }
    public string ProducerId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Address { get; set; }
    ...

    public List<dynamic> Information { get; set; }
}

We will be receiving this through a Web API POST. So I have this controller signature:

[HttpPost]
    public void Post([FromBody] dynamic value)
    {
        var converter = new ExpandoObjectConverter();
        dynamic input = JsonConvert.DeserializeObject<Loan>(value,converter);


    }

But when I run this code, NewtonSoft keeps giving me the error

Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 'The best overloaded method match for 'Newtonsoft.Json.JsonConvert.DeserializeObject<ExpandoObjectTestAPI.Models.Loan>(string, params Newtonsoft.Json.JsonConverter[])' has some invalid arguments'

Looking around it appears that it is having problem with the dynamic type that is passed in. So how would I pass in this JSON so I can parse it using the ExpandoObjectConverter?

Answer 1

This doesn't answer the question using dynamic, but it's worth considering avoiding this by using a Dictionary instead to model custom properties. The following works for generic key/value pairs:

public class Applicant
{
   ...Standard properties

   public IDictionary<string, object> Custom { get; set; }
}

It would accept JSON with arbitrary dynamic fields nested under your "Custom" namespace:

{
    "applicationId": "123",
    "producerId": "456",
    "custom": {
        "favoriteAnimal": "turtles",
        "someRandomMetadata": 42,
        "someUnforeseenList": ["foo", "bar"]
    }
 }

I've had good luck handling user-defined extension fields this way. It also has the arguable advantage of isolating custom fields into a nested namespace to isolate from built-in data.