using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        TraverseAndRemove();

    }

    static void TraverseAndRemove()

    {

        var keys = new string[] { "a", "b", "c", "e" };

        var json = @"

        {

            a: 1,

            b: 2,

            c: {

                d: 1,

                e: 2

            }

        }

        ";

        var root = JObject.Parse(json);

        var descendants = root.DescendantsAndSelf().ToList();

        foreach (var d in descendants)

        {

            var jProp = d as JProperty;

            if (jProp != null && !keys.Contains(jProp.Name))

                jProp.Remove();

        }

        Console.WriteLine(JsonConvert.SerializeObject(root, Formatting.Indented).ToString());

    }

}

​