using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        var json = @"{

          ""someProperties"" : ""someValues"",

          ""$ROOT_QUERY.searchResults({\""path\"":\""/some/url\""}).features"": 

          {

            ""propertyOtherA"": ""valueA"",

            ""propertyOtherB"": ""null"",

          },

          ""$ROOT_QUERY.searchResults({\""path\"":\""/some/url\""}).otherText"": 

          {

            ""propertyOtherA"": ""valueA"",

            ""propertyOtherB"": ""null"",

          }

        }";

        // using SelectToken

        var parsed = JObject.Parse(json);

        var someUrl = "/some/url";

        var path = "['$ROOT_QUERY.searchResults({\"path\":\"" + someUrl + "\"}).features']";

        var token = parsed.SelectToken("$." + path);

        Console.WriteLine(token);

        // using subscript

        var simplePath = "$ROOT_QUERY.searchResults({\"path\":\"/some/url\"}).features";

        Console.WriteLine(parsed[simplePath]);

    }

}