using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    private static readonly PostService _postService = new PostService();

    public static void Main()

    {       

        var allPosts = _postService.GetAll().ToList();

        Console.WriteLine("Posts criados na \"base de dados\":");

        foreach(var post in allPosts)

        {

            Console.WriteLine("Post: " + post.Id);

        }

        // Irá pegar 3 Ids validos "randomicamente"

        var module_Highlights = allPosts

            .OrderBy(p => p.Id)

            .Skip(1).Take(9).Skip(1).Take(8).Skip(1).Take(3).ToList()

            .OrderByDescending(p => p.Id)

            .Select(p => p.Id.ToString()).ToArray();

        Console.WriteLine("");

        Console.WriteLine("Ids selecionados:");

        foreach(var id in module_Highlights)

        {

            Console.WriteLine("Id: " + id);

        }

        // Faz a consulta normalmente

        var posts = _postService.Find(module_Highlights).ToList();

        // Reordena de acordo com os ids usados na pesquisa

        for (var i = module_Highlights.Length-1; i >= 0; i--)

        {

            var id = module_Highlights[i];

            var post = posts.Single(p=>p.Id.ToString().Equals(id));

            // usa a tecnica de pop and push para evitar memory leak

            posts.Remove(post);

            posts.Insert(0, post);

        }

        Console.WriteLine("");

        Console.WriteLine("Resultado final:");

        foreach(var post in posts)

        {

            Console.WriteLine("Post: " + post.Id);

        }

    }       

}

​

public class PostService

{

    private readonly Post[] _allPosts;

    public PostService()

    {

        _allPosts = new [] 

        {

            new Post(),

            new Post(),

            new Post(),

            new Post(),

            new Post(),

            new Post(),

            new Post(),

            new Post(),

            new Post(),

            new Post()

        };

    }

    public IEnumerable<Post> GetAll()

    {

        return _allPosts;

    }

​

    public IEnumerable<Post> Find(string[] ids)

    {

        return _allPosts.Where(p=> ids.Contains(p.Id.ToString()));

    }

}

​

public class Post

{

    public Guid Id { get; set; }

    public Post() 

    {

        Id = Guid.NewGuid();

    }

}