using System;

using System.Collections.Generic;

using System.Linq;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string json = @"

            {

              ""Id"": 1,

              ""Description"": ""This is the ${root} of the ${tree}."",

              ""Children"": [

                {

                  ""Id"": 2,

                  ""Description"": ""This is first ${child} of the ${root}."",

                  ""Children"": [

                    {

                      ""Id"": 4,

                      ""Description"": ""Some ${node}s in the ${tree} are deeply nested, like this one."",

                      ""Children"": []

                    },

                    {

                      ""Id"": 5,

                      ""Description"": ""They say money is the ${root} of all evil."",

                      ""Children"": []

                    }

                  ]

                },

                {

                  ""Id"": 3,

                  ""Description"": ""This is the second ${child} of the ${root}"",

                  ""Children"": [

                    {

                      ""Id"": 6,

                      ""Description"": ""You wouldn't want to chop down this ${tree}."",

                      ""Children"": []

                    },

                    {

                      ""Id"": 7,

                      ""Description"": ""This ${root} of the ${tree} is two levels below this ${node}."",

                      ""Children"": []

                    }

                  ]

                }

              ]

            }";

​

        Dictionary<string, string> placeholders = new Dictionary<string, string>

        {

            { "${root}", "bottom-most ${node}" },

            { "${child}", "immediate descendant ${node}" },

            { "${tree}", "hierarchy" },

            { "${node}", "item" },

        };

​

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

        ReplacePlaceholderValues(root, placeholders);

        Console.WriteLine(root.ToString());

    }

    public static void ReplacePlaceholderValues(JContainer root, Dictionary<string, string> placeholders)

    {

        var jValues = root.Descendants()

                          .OfType<JValue>()

                          .Where(jv => jv.Type == JTokenType.String);

​

        foreach (var jVal in jValues)

        {

            jVal.Value = ReplacePlaceholderValues((string)jVal.Value, placeholders);

        }

    }

​

    public static string ReplacePlaceholderValues(string source, Dictionary<string, string> placeholders)

    {

        var replacedText = placeholders.Aggregate(source, (current, replacement) =>

        {

            return current.Replace(replacement.Key, replacement.Value);

        });

        return replacedText;

    }

}