DataSet ds = Api.Zselect(MercatorUi.Globals.RepData, "select top 1 * from CLI order by c_id");
if ((ds != null) && (ds.Tables[0].Rows.Count >= 1))
{
    Api.TrimEndDataTable(ds.Tables[0]);
    MercatorDatabase.CLI cli = new MercatorDatabase.CLI(ds.Tables[0].Rows[0]);
    string nom = cli.C_NOM;
    ...
}