using System;

using System.Linq;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string json = @"

        {

            ""country"": ""USA"",

            ""date"": ""2019-06-30"",

            ""Speaker"": [

                {

                    ""id"": ""name"",

                    ""value"": ""Tiger""

                },

                {

                    ""id"": ""age"",

                    ""value"": ""35""

                },

                {

                    ""id"": ""topic"",

                    ""value"": "".NET""

                }

            ]

        }";

​

        JObject root = JObject.Parse(json);

        JProperty arrayProp = root.Properties()

                                  .Where(jp => jp.Value.Type == JTokenType.Array)

                                  .FirstOrDefault();

        if (arrayProp != null)

        {

            foreach (JObject item in arrayProp.Value.Children<JObject>())

            {

                root[(string)item["id"]] = item["value"];

            }

            arrayProp.Remove();

        }

​

        json = root.ToString();

        Console.WriteLine(json);

    }

}