conex.Open();
NpgsqlCommand coman = new NpgsqlCommand("SELECT pid,usename,application_name,datname,client_addr,backend_start,state,query_start,xact_start,wait_event,query FROM pg_stat_activity ORDER BY query_start DESC", conex);
                NpgsqlDataReader dat = coman.ExecuteReader();
                while (dat.Read())
                {
                    Entidades obj = new Entidades();
                    if (obj == null || obj !=null)

                    {
                    obj.pid = Convert.ToInt32(dat["pid"]);
                        obj.usename = Convert.ToString(dat["usename"]);
                        obj.appcationName = Convert.ToString(dat["application_name"]);
                        obj.datname = Convert.ToString(dat["datname"]);
                        obj.client_ddr = Convert.ToString(dat["client_addr"]);
                        obj.backed_star = Convert.ToDateTime(dat["backend_start"]);
                        obj.state = Convert.ToString(dat["state"]);
                        obj.query_star = Convert.ToDateTime(dat["query_start"]);
                        obj.Xact_star = Convert.ToDateTime(dat["xact_start"]);
                        obj.waiting = Convert.ToString(dat["wait_event"]);
                        obj.query = Convert.ToString(dat["query"]);
                        dic.Add(obj.pid, obj);
if (!dic.ContainsKey(obj.pid))//si el dic no contieene el id agregar
                            {
                                dic.Add(obj.pid, obj);

                            }
                            else
                            {
                                dic[obj.pid].query_star = obj.query_star; //actualiza tiempo de ejecucion

                            }