using static System.Convert;

using static System.Console;

using System.Collections.Generic;

using System.Linq;

public class Program {

    public static void Main() {

        List<Ata> lstAtas = new List<Ata>() {

                new Ata{ NroAta = "1"},

                new Ata{ NroAta = "10"},

                new Ata{ NroAta = "6"},

                new Ata{ NroAta = "4"},

                new Ata{ NroAta = "5"},

                new Ata{ NroAta = "2"},

                new Ata{ NroAta = "3"},

        };

        foreach (var ata in lstAtas.OrderBy(x => ToInt32(x.NroAta))) WriteLine(ata.NroAta);

    }

}

public class Ata {

    public string NroAta;

}