How to deserialize collection with different types?

Question

I have a JSON feed that looks like this (I removed some fields that aren\'t necessary for this example):

{
  \"total_count\": 2,
  \"num_pages\": 1,
  \"curr         


        

Answer 1

Your question is essentially a duplicate of this one, and the solution is the same. You need a JsonConverter to instantiate the correct object. However, there are a couple of differences that I see.

If you look at the converter implementation from the other answer, you can see that it looks for a boolean flag in the JSON to determine the type to instantiate. In your case, there is not such a flag, so you'd need to use the existence or absence of a field to make this determination. Also, your list of transactions in the JSON is actually a list of objects that contain transactions, so the converter needs to account for that as well.

With these changes, your converter should look something like this:

public class TransactionConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return typeof(Transaction).IsAssignableFrom(objectType);
    }

    public override object ReadJson(JsonReader reader, 
        Type objectType, object existingValue, JsonSerializer serializer)
    {
        JToken transaction = JToken.Load(reader)["transaction"];
        if (transaction["recipient"] != null)
        {
            return transaction.ToObject<InternalTransaction>();
        }
        else
        {
            return transaction.ToObject<ExternalTransaction>();
        }
    }

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

assuming that your classes are defined like this:

class TransactionPagedResult
{
    [JsonProperty(ItemConverterType=typeof(TransactionConverter))]
    public IEnumerable<Transaction> Transactions { get; set; }
}

class Transaction
{
    public string Id { get; set; }
    [JsonProperty("created_at")]
    public DateTime CreatedAt { get; set; }
}

class InternalTransaction : Transaction
{
    public User Recipient { get; set; }
}

class ExternalTransaction : Transaction
{
    public string Hsh { get; set; }
    [JsonProperty("recipient_address")]
    public string RecipientAddress { get; set; }
}

class User
{
    public string Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
}

Also, to answer the last part of your question, if you decorate your list with a [JsonConverter] attribute, the converter is expected to handle the entire list. To handle the individual items, you need to use [JsonProperty(ItemConverterType=typeof(TransactionConverter))] on the list instead. I've edited the class definitions above to make this clear.