REST API Response with property sometimes get a list or an object

Question

I am calling the same REST API and from that API I am getting a response as a JSON object, and while trying to deserialize it, it throws an error because one of the objects sometimes returns as a list or an object.

I have shown some sample codes in which Address is sometimes returned as a list and sometimes as a single object.

JSON object which returns Address with list:

{
  "ResponseStatus": {
    "Code": "1",
    "Description": "Success"
  },
  "Address": [
    {
      "City": "CLEVELAND",
      "State": "OH",
      "PostalCode": "44126",
      "CountryCode": "US"
    },
    {
      "City": "CLEVELAND",
      "State": "WV",
      "PostalCode": "26215",
      "CountryCode": "US"
    }
  ]
}

JSON object which returns Address as an object:

{
  "ResponseStatus": {
    "Code": "1",
    "Description": "Success"
  },
  "Address": {
    "City": "CLEVELAND",
    "State": "OH",
    "PostalCode": "44126",
    "CountryCode": "US"
  }
}

The class I am using to deserialize the JSON object:

public class Address
{
    public string City { get; set; }
    public string State { get; set; }
    public string PostalCode { get; set; }
    public string CountryCode { get; set; }
}

public class ResponseStatus
{
    public string Code { get; set; }
    public string Description { get; set; }
}

public class Response
{
    public ResponseStatus ResponseStatus { get; set; }
    public List<Address> Address { get; set; }
}

Response result = JsonConvert.DeserializeObject<Response>(response);

Response: This variable is getting initialized after the REST API is called.

Answer 1

You should implement a Custom Json Converter to handle data with different types.

With the below example, to handle the Address which possibly is an array or object.

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

public class ObjectListConverter<T> : JsonConverter
    where T : class, new()
{
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        JToken t = JToken.FromObject(value);
        t.WriteTo(writer);
    }

    public override List<T> ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.StartArray)
        {
            return JToken.Load(reader).ToObject<List<T>>();
        }
        else if (reader.TokenType == JsonToken.StartObject)
        {
            return new List<T> { JToken.Load(reader).ToObject<T>() };
        }
        else if (reader.TokenType == JsonToken.Null)
        {
            return null;
        }
        
        throw new JsonException();
    }
    
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(List<T>) || objectType == typeof(T);
    }
}

Add the ObjectListConverter into the JsonConverterAttribute.

public class Response
{
    public ResponseStatus ResponseStatus { get; set; }
    
    [JsonConverter(typeof(ObjectListConverter<Address>))]
    public List<Address> Address { get; set; }
}