Deserializing to DynamicObject Using Json.NET

Question

If I want to deserialize to an ExpandoObject using Json.NET, I can do the following:

var obj2 = JsonConvert.DeserializeObject<ExpandoObject>(serializedData, new ExpandoObjectConverter());

But because I need to get back an object with a certain interface out of deserialization, I need to use a DynamicObject instead of ExpandoObject:

   public interface ISomeInterface
    {
        public string InterfaceMember { get; set; }
    }

    public class SomeClass: ISomeInterface
    {
        public int X { get; set; }
        public string InterfaceMember { get; set; }
    }

    public class SomeClass2 : DynamicObject, ISomeInterface
    {
        public string InterfaceMember { get; set; }
    }

But when I do the following, I get an error:

       var obj = new SomeClass
        {
            InterfaceMember = "xyz",
            X = 3
        };

        string serializedData = JsonConvert.SerializeObject(obj);

        SomeClass2 obj2 = JsonConvert.DeserializeObject<SomeClass2>(serializedData, new ExpandoObjectConverter());

And the error is:

'SomeClass2' does not contain a definition for 'X'

How can I make it work for a DynamicObject?

NOTE: I am providing the concrete class SomeClass here just for the sake of the example. At runtime, it can actually be any type implementing ISomeInterface. So, I cannot deserialize directly to SomeClass. My actual goal is to deserialize to ISomeInterface.

Serializing to an arbitrary type implementing a certain interface still doesn't mandate using DynamicObject. You can just use the overload that takes a Type at runtime (providing the actual type, and casting to ISomeInterface afterwards). — Jeroen Mostert
– Jeroen Mostert, Commented Oct 2, 2019 at 12:59
It's because TryGetMember for X return false ... if you would override it (both TryGet/TrySet) then this would work — Selvin
– Selvin, Commented Oct 2, 2019 at 13:09
dotnetfiddle.net/0ml3L0 also SomeClass2 has no definition of X at compile time ... so obviosuly for variable of type SomeClass2 is not valid to ask about property X ... but for dynamic it is valid — Selvin
– Selvin, Commented Oct 2, 2019 at 13:15
@Selvin I tried your solution and it works for creating this dynamic object. But when I serialize it again, it creates an empty object: Console.WriteLine(JsonConvert.SerializeObject(t)); — hakanviv
– hakanviv, Commented Oct 2, 2019 at 14:37

hakanviv · Accepted Answer · 2019-10-02 15:58:12Z

The following code for SomeClass2 solves the problem (thanks to @Selvin's comment and sample fiddle):

public class SomeClass2 : DynamicObject, ISomeInterface
{
    private Dictionary<string, object> dictionary = new Dictionary<string, object>();

    [JsonProperty]
    public string InterfaceMember { get; set; }

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        return dictionary.TryGetValue(binder.Name, out result);
    }

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        dictionary[binder.Name] = value;
        return true;
    }

    public override IEnumerable<string> GetDynamicMemberNames()
    {
        return dictionary.Keys;
    }
}

I just added the GetDynamicMemberNamesoverride and added [JsonProperty] attribute to the InterfaceMember property so that reserializing the deserialized dynamic object will not be empty.

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