如何使用sql查询从数据集中获取行？

i need to take some row. They came from sql TARIH (sql column) is smalldatetime format. But give me error : DataRow[] rows = dsChart.Tables[0].Select("TARIH<='" + datestart + " " + txtStartDateTime.Text + "' and TARIH>='" + dateend + " " + txtEndDateTime.Text+"'"); i need to take some row. They came from sql TAR