using System;

using System.Collections.Generic;

using System.Linq;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string json = @"

            {

              ""property1"": ""value1"",

              ""property2"": 2,

              ""property3"": true,

              ""property4"": {

                ""myArray"": [

                  {

                    ""arrayProperty1"": ""im the first object in array"",

                    ""arrayProperty2"": ""some value""

                  },

                  {

                    ""arrayProperty1"": ""im the second object in array"",

                    ""arrayProperty2"": ""some value""

                  }

                ]

              }

            }";     

​

        string json1 = AddPrefixToAllKeys(json, "mynamespace.");

        Console.WriteLine(json1);

​

    }

    public static string AddPrefixToAllKeys(string json, string prefix)

    {

        JContainer token = (JContainer)JToken.Parse(json);

​

        // Note: We need to process the descendants in reverse order here

        // to ensure we replace child properties before their respective parents

        foreach (JProperty prop in token.Descendants().OfType<JProperty>().Reverse().ToList())

        {

            prop.Replace(new JProperty(prefix + prop.Name, prop.Value));

        }

        return token.ToString();

    }

}