using System;

using System.Collections.Generic;

using System.Linq;

class Item {

    public int Id {get;set;}

    public string Status {get;set;}

}

class Items: List<Item> 

{

    public Items() 

    {

        Add(new Item { Id = 1, Status = "Aguardando Atendimento" });

        Add(new Item { Id = 2, Status = "Atendimento encerrado" });

        Add(new Item { Id = 3, Status = "Em atendimento" });

        Add(new Item { Id = 4, Status = "Atendimento encerrado" });

        Add(new Item { Id = 5, Status = "Aguardando Atendimento" });

    }

}

class StatusComparer : IComparer<string>

{

    private Dictionary<string, string> Filters = new Dictionary<string, string>(3);

    public StatusComparer()

    {

        Filters.Add("Aguardando Atendimento", "a");

        Filters.Add("Em atendimento", "b");

        Filters.Add("Atendimento encerrado", "c");

    }

    public int Compare(string x, string y)

    {

        string aX = Filters[x];

        string yX = Filters[y];

        return aX.CompareTo(yX);

    }

}

public class Program

{

    public static void Main()

    {   

        //"Aguardando Atendimento"

        //"Em atendimento"

        //"Atendimento encerrado"

        Items items = new Items();

        var ordenado = items.OrderBy(x => x.Status, new StatusComparer());              

        foreach(var c in ordenado)

        {

            Console.WriteLine("{0} - {1}", c.Id, c.Status);

        }

    }

}