using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using Newtonsoft.Json.Serialization;

public class Program

{

    public static void Main()

    {

        var myClass = new MyClass

        {

            CamelCaseThis = new Dictionary<string, ICollection<string>>

            {

                { "ABC1", new List<string> { "FOO", "Bar" } },

                { "DEF2", new List<string> { "Baz", "QuuX" } },

                { "ShouldBeAllLower3", new List<string> { "Blah" } },

            }

        };

​

        string json = JsonConvert.SerializeObject(myClass, Formatting.Indented);

        Console.WriteLine(json);

    }

}

​

[JsonObject(NamingStrategyType = typeof(CustomNamingStrategy))]

public class MyClass

{

    public Dictionary<string, ICollection<string>> CamelCaseThis { get; set; }

}

​

public class CustomNamingStrategy : CamelCaseNamingStrategy

{

    public CustomNamingStrategy()

    {

        ProcessDictionaryKeys = true;

        ProcessExtensionDataNames = true;

        OverrideSpecifiedNames = true;

    }

​

    public override string GetDictionaryKey(string key)

    {

        return key.ToLower();

    }

}

​