为何无返回的数据？

//界面层代码
            HIS.BLL.publicsqltagBll sqltag=new publicsqltagBll();            this.textEdit_sex.Properties.DataSource = sqltag.GetList(91, "", "", "", "");
            this.textEdit_sex.Properties.DisplayMember = "名称";
            this.textEdit_sex.Properties.ValueMember = "性别码";
            this.textEdit_sex.Properties.NullText = "";
//BLL层代码
        public DataSet GetList(int strtagno, string strwhere1, string strwhere2, string strwhere3, string strwhere4)
{
            return dal.GetList(strtagno,  strwhere1,  strwhere2,  strwhere3,  strwhere4);
}
//Dal代码
        public DataSet GetList(int strtagno, string strwhere1, string strwhere2, string strwhere3, string strwhere4)
{
            string strsql = "SELECT sql FROM wh_tag_sql WHERE tag="+strtagno.ToString();
            Database db = DatabaseFactory.CreateDatabase();
            object obj = db.ExecuteScalar(CommandType.Text, strsql);            StringBuilder strSql1 = new StringBuilder();
            strSql1 = strSql1.Append(obj.ToString());
            strSql1.Replace(":py_code", "'" + strwhere1 + "%'");
            strSql1.Replace(":d_code", "'" + strwhere2 + "%'");
            strSql1.Replace(":code", "'" + strwhere3 + "%'");
            strSql1.Replace(":name", "'" + strwhere4 + "%'");            Database db1 = DatabaseFactory.CreateDatabase();
return db1.ExecuteDataSet(CommandType.Text, strSql1.ToString());
}请叫高手，界面层this.textEdit_sex中为何无返回的数据？