un piccolo esempio, migliorabile sicuramente

codice:
string strQuery = @"SELECT  t_anno_corrente AS tac,
                            t_anno_precedente AS tap,
                            tot_anno_precedente AS tot
                    FROM miaTabella 
                    ORDER BY ID DESC;";

OdbcCommand objCmd = new OdbcCommand(strQuery, myConnectionString);
objCmd.CommandType = CommandType.Text;
objCmd.CommandText = strQuery;

List<string> risultati = new List<string>();
using (OdbcDataReader dr = objCmd.ExecuteReader(CommandBehavior.CloseConnection))
{
    while (dr.Read())
    {
        risultati.Add(string.Concat(dr[0].ToString(), ",", dr[1].ToString(), ",", dr[2].ToString()));
    }
}
//qui puoi usare risultati