Почему datetimepicker выбирает максимум 1 день в выборе?

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Datetimepicker from и datetimepicker to....

Работа только на один день exp, 16.03.2018.... 16.03.2018

Работать отлично

Если выбрать с 01.03.2018 по 16.03.2018 не получится...

В чем я ошибся?

Что я уже пробовал:

<pre>private void radni_sati2()
        {

            String cs = "Data Source=.\\SQLEXPRESS;Initial Catalog=bss_prijava_radnika;Integrated Security=True";
            using (SqlConnection openCon = new SqlConnection(cs))

            {


                string saveStaff = "SELECT a.IdPrijava, a.redni_broj , a.radnik, isnull(convert(varchar(20), a.vrijemeodjave, 113), '') as vrijemeodjave, convert(varchar(20), b.vrijemeprijave, 113) as vrijemeprijave, "
                    + "CASE WHEN (DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) > 8 THEN 8 ELSE(DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) END  AS radni_sati, "
                    + "CASE WHEN(DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) > 8  THEN(DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) - 8  ELSE NULL END  AS prekovremeni "
                    + "FROM(SELECT IdPrijava, redni_broj, radnik, vrijemeodjave, ROW_Number() OVER(Partition By IdPrijava ORDER BY vrijemeprijave) as RowNum "
                    + "FROM dbo.prijava_radnika) a INNER JOIN(SELECT IdPrijava, redni_broj, radnik, vrijemeprijave, (ROW_Number() OVER(Partition By IdPrijava ORDER BY vrijemeprijave) - 1) as RowNumMinusOne FROM dbo.prijava_radnika) b ON a.IdPrijava = b.IdPrijava where 1 = 1 ";

                if (!string.IsNullOrEmpty(textBox1.Text))
                {
                    saveStaff += " AND a.radnik LIKE \'%" + textBox1.Text + "%\' ";
                }


                if (checkBox1.Checked)
                {
                    String strFilterDTP1 = dateTimePicker1.Value.ToString("yyyy-MM-dd");
                    String strFilterDTP2 = dateTimePicker2.Value.ToString("yyyy-MM-dd");

                    saveStaff += " AND b.vrijemeprijave between '" + strFilterDTP1 + " 00:00:00' AND '" + strFilterDTP1 + " 23:59:59' ";
                    saveStaff += " AND a.vrijemeodjave between '" + strFilterDTP2 + " 00:00:00' AND '" + strFilterDTP2 + " 23:59:59' ";
                }

                String someDate = "25 Mar 2018 13:13:00";
                DateTime someDT = DateTime.Parse(someDate);

                Console.WriteLine(saveStaff);

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