using System;

using System.Collections.Generic;

using System.Linq;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        MyData data = new MyData();

        Newtonsoft.Json.JsonSerializerSettings settings = new Newtonsoft.Json.JsonSerializerSettings

        {

            Converters = new List<JsonConverter>() { new TrimNullListValues() }

        };

        string jsonString = @"{""ListData"": [{""source"" : 10 , ""target"" : 20}, null]}";

        JsonConvert.PopulateObject(jsonString, data, settings);

        data.Dump();

    }

}

​

public class TrimNullListValues : JsonConverter

{

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

    {

        serializer.Serialize(writer, value);

    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

    {

        JArray array = JArray.Load(reader);

        foreach (JToken item in array.ToList())

        {

            if (item.Type == JTokenType.Null)

                item.Remove();

        }

        return array.ToObject(objectType);

    }

    public override bool CanConvert(Type objectType)

    {

        return objectType.IsGenericType && objectType.GetGenericTypeDefinition() == typeof(List<>);

    }

}

​

public class MyData

{

    public class MyNestedData

    {

        public int Source;

        public int Target;

    }

    public List<MyNestedData> ListData;

}

​