Transform json objects in .NET using JSON.NET

JsonTransformation.cs

using System;
using Newtonsoft.Json.Linq;

namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            var original = JObject.Parse(@"{
               'FirstName': 'John', 
               'LastName': 'Smith',
               'Enabled': false,
               'Roles': [ 'User' ],
               'Results' : [ 1, 2, 3] }");
            
            var template = JObject.Parse(@"{
              'FirstName': '',
              'Role' : '$.Roles[0]' }");

            var result = Process(original, template);

            Console.WriteLine(result.ToString());
        }

        private static JObject Process(JObject original, JObject template)
        {
            var result = new JObject();

            foreach (var property in template.Properties())
            {
                var value = property.Value?.ToString();

                var path = value?.StartsWith("$") == true
                    ? value
                    : property.Path;

                var selected = original.SelectToken(path);
                result.Add(property.Name, selected);
            }

            return result;
        }
    }
}

Result is:

{
    "FirstName": "John",
    "Role": "User"
}