using System;

using System.Linq;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string jsonString = @"

            {

              ""data"": {

                ""app_settings"": {

                  ""jbofmngeodhmdlnicmlnfhjmmbdbcokh"": {

                    ""title"": ""app 1"",

                    ""description"": ""desc 1"",

                    ""custom_app_setting_stored_below"": ""asd"",

                    ""cust1"": 3,

                    ""cust2"": false

                  },

                  ""esghmzlnxcfpnrkbokmvgtjmcaknysdb"": {

                    ""title"": ""app 2"",

                    ""description"": ""desc 2"",

                    ""custom_app_setting_stored_below"": ""asd"",

                    ""cust8"": 12,

                    ""cust10"": ""11/25/2013"",

                    ""cust11"": ""nothing"",

                    ""cust12"": true,

                    ""cust13"": 3

                  }

                }

              }

            }";

        string extensionToBlacklist = "app 1";

        JObject json = JObject.Parse(jsonString);

        JToken data = json["data"];

        JToken app_settings = data["app_settings"];

        foreach (JProperty extensionProperty in app_settings)

        {

            JObject extensionObject = (JObject)extensionProperty.Value;

            if ((string)extensionObject["title"] == extensionToBlacklist)

            {

                extensionObject.Add("blacklist", true);

            } 

        }

        Console.WriteLine(json.ToString());

    }

}