How to Ignoring Fields and Properties Conditionally During Serialization Using JSON.Net?

Question

How to Ignoring Fields and Properties Conditionally During Serialization Using JSON.Net? I can't inherit from JsonIgnoreAttribute because it's a sealed class. What should I do?

Answer 1

You can use JSON.NET's ShouldSerialize-syntax. There's a good example on JSON.NET site:

http://www.newtonsoft.com/json/help/html/ConditionalProperties.htm

public class Employee
{
    public string Name { get; set; }
    public Employee Manager { get; set; }

    public bool ShouldSerializeManager()
    {
        // don't serialize the Manager property if an employee is their own manager
        return (Manager != this);
    }
}

If ShouldSerialize doesn't fit your needs, you can take full control of the serialization with the ContractResolvers: http://www.newtonsoft.com/json/help/html/ContractResolver.htm

Answer 2

I found the answer. I inherit from JsonConverter and create a new convertor.

public class CustomJsonConverter : JsonConverter
{
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var list = (IList)value;

        JArray s = new JArray();

        foreach (var item in list)
        {
            JToken token = JToken.FromObject(item);
            JObject obj = new JObject();

            foreach (JProperty prop in token)
            {
                if (prop.Name != "Title") // your logic here
                    obj.Add(prop);
            }

            s.Add(obj);
        }

        s.WriteTo(writer);

    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotImplementedException("Unnecessary because CanRead is false. The type will skip the converter.");
    }

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

    public override bool CanConvert(Type objectType)
    {
        return objectType != typeof(IList);
    }
}