using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/56638368/sort-by-most-occurring-string-from-json-by-key-order-and-order-contains-array-it?noredirect=1

​

    public class Order 

    {

        public string[] order { get; set; }

    }

​

    public class IEnumerableComparer<TEnumerable, TElement> : IEqualityComparer<TEnumerable> where TEnumerable : IEnumerable<TElement>

    {

        //Adapted from IEqualityComparer for SequenceEqual

        //https://stackoverflow.com/questions/14675720/iequalitycomparer-for-sequenceequal

        //Answer https://stackoverflow.com/a/14675741 By Cédric Bignon https://stackoverflow.com/users/1284526/c%C3%A9dric-bignon 

        public bool Equals(TEnumerable x, TEnumerable y)

        {

            return Object.ReferenceEquals(x, y) || (x != null && y != null && x.SequenceEqual(y));

        }

​

        public int GetHashCode(TEnumerable obj)

        {

            // Will not throw an OverflowException

            unchecked

            {

                return obj.Where(e => e != null).Select(e => e.GetHashCode()).Aggregate(17, (a, b) => 23 * a + b);

            }

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var jsonString = GetJson();

            var items = JsonConvert.DeserializeObject<List<Order>>(jsonString);

            var query = items

                //If order items aren't already sorted, you may need to do so first.

                //use StringComparer.OrdinalIgnoreCase or StringComparer.Ordinal or StringComparer.CurrentCulture as required.

                .Select(i => i.order.OrderBy(s => s, StringComparer.Ordinal).ToArray()) 

                //Adapted from writing a custom comparer for linq groupby

                //https://stackoverflow.com/questions/37733773/writing-a-custom-comparer-for-linq-groupby

                //Answer https://stackoverflow.com/a/37734601 by Gert Arnold https://stackoverflow.com/users/861716/gert-arnold

                .GroupBy(s => s, new IEnumerableComparer<string [], string>())

                .OrderByDescending(g => g.Count())

                .SelectMany(g => g)

                .Select(a => new Order { order = a });

            var sortedItems = query.ToList();

            Console.WriteLine(JsonConvert.SerializeObject(sortedItems, Formatting.Indented));

        }   

        static string GetJson()

        {

            var json = @"[{ ""order"":[""Order1""]},{ ""order"":[""Order2""]}, { ""order"":[""Order2"", ""Order3""]}, { ""order"":[""Order1"", ""Order2""]}, { ""order"":[""Order2"", ""Order3""]}]

";

            return json;

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: " + Environment.Version);

            Console.WriteLine("Json.NET version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​