using Newtonsoft.Json;

using System;

using System.Collections.Generic;

using System.Linq;

​

public class VegetablesPriceNode

{

    public string Country { get; set; }

    public Dictionary<string, string> VegetableDictionary { get; set; }

}

​

public class Program

{

    public static void Main()

    {

        var json = "[{\"Country\":\"Afghanistan\",\"VegetableDictionary\":{\"Onions\":\"$1.00\",\"Potatoes\":\"$1.40\"}},{\"Country\":\"Bahrain\",\"VegetableDictionary\":{\"Onions\":\"$3.00\",\"Potatoes\":\"$3.40\"}}]";

​

        var vegetablesPriceNodeList = JsonConvert.DeserializeObject<List<VegetablesPriceNode>>(json);

​

        var obj = vegetablesPriceNodeList

            .SelectMany(x =>

                x.VegetableDictionary

                    .Select(x => x.Key)

            )

            .Distinct()

            .Select((k) =>

                vegetablesPriceNodeList

                    .Select(v => v.VegetableDictionary[k])

                    .Prepend(k)

                    .ToArray()

            ).ToArray();

​

        var output = JsonConvert.SerializeObject(obj);

        Console.WriteLine(output);

    }

}