Return Values from a List c #

Good, I would like you to help me.

I am commenting that I am doing a webservice that returns me in a List , I am using Dos Capas in: 1.Web Service 2.Capa Datos

The Code of my Webservice is the following:

public class Heldesk : System.Web.Services.WebService
    {
        D_Usp_LlenarCombos obj = new D_Usp_LlenarCombos();
        [WebMethod]
        public List<Combos> Ws_LlenarCombo(Int32 Opt,Int32 Id_Tipo)
        {
            return obj.D_LlenarCombo(Opt, Id_Tipo);
        }
    }

Create a Data Class to attach to the List < > that has the following:

public class Combos
    {
        public string Id { get; set; }
        public Int32 Nombre { get; set; }
    }

and in my data layer the following:

  public List<Combos> D_LlenarCombo(Int32 Opt, Int32 Id_Tipo)
    {
        SqlDataReader reader;

        SqlConnection cn = new SqlConnection(ObtenerCadenaConexion());
        cn.Open();
        SqlCommand cmd = new SqlCommand("LlenarCombo", cn);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add("@opt", SqlDbType.Int).Value = Opt;
        cmd.Parameters.Add("@Id_Tipo", SqlDbType.Int).Value = Id_Tipo;

        reader= cmd.ExecuteReader();
        List<Combos> Combo = new List<Combos>();
        try
        {
            while (reader.Read())
            {

                Combo.Add(reader.GetValue(0), reader.GetValue(1));

            }
            reader.Close();
            cmd.Dispose();
            cn.Close();
            return D_LlenarCombo(Opt, Id_Tipo);
        }
        catch (Exception Ex)
        {
            throw new Exception(Ex.Message);
        }

This is my Procedure:

create procedure llenarcombos
@opt int,
@Id_Tipo int
as
if @opt=1
begin
select Id_Tipoincidencia,TipoIncidencia from Ms_TipoIncidencia

end

What I want is for you to vote for this result

Id_Tipoincidencia      TipoIncidencia
    1                  Incidencia de Aplicativo
    2                  Bank Plus
    3                  Base de datos

The problem that I do not get the results, I vote this error.

If you could help me.

What I really want is to consume that service and add it in a combobox