protected void Btn_addWorkingTimeAdd_Click(object sender, EventArgs e)
        {
            con.Open();
            SqlCommand cmd = con.CreateCommand();

            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "INSERT INTO [STUDENT_WORKING_TIME] ([STUDENT_ID], [STUDENT_FIRSTNAME], [STUDENT_LASTNAME], [WORKING_DEPARTMENT], [WORK_DESCRIPTION], [START_WORKING_TIME], [END_WORKING_TIME], [WORK_HOURS], [WORKING_DATE], [STUDY_TERMS], [STUDY_YEARS], [CREATE_TIMESTAMP], [APPROVE_STATUS]) VALUES ('" + Tb_addWorkingTimestudentID.Text + "', N'" + Tb_addWorkingTimeStudentFirstname.Text + "', N'" + Tb_addWorkingTimeStudentLastname.Text + "', N'" + Ddl_addWorkingTimeDepartmentName.Text + "', N'" + Tb_addWorkingTimeDescription.Text + "', '" + Tb_addWorkingTimeStartTime.Text + "', '" + Tb_addWorkingTimeEndTime.Text + "', '" + Tb_addWorkingTimeHours.Text + "', '" + Tb_addWorkingTimeDate.Text + "', '" + Ddl_addWorkingTimeStudyYear.Text + "', '" + Ddl_addWorkingTimeStudyYears.Text + "', '" + DateTime.Now + "','Waiting')";
            cmd.ExecuteNonQuery();

            con.Close();

            Gv_STUDENT_WORKING_TIME.DataBind();
            ScriptManager.RegisterStartupScript(Page, Page.GetType(), "addWorkingTimeModalCenter", "$('#addWorkingTimeModalCenter').modal('hide');", true);
        }
        protected void Btn_addWorkingTimeSearch_Click(object sender, EventArgs e)
        {
            Thread.Sleep(1000);
            string STUDENT_ID = Tb_addWorkingTimeFilter.Text;
            string Filter     = "";

            //Colum of data table
            if (STUDENT_ID != "")
            {
                Filter = Filter + "STUDENT_ID like '%" + STUDENT_ID + "%' and ";
            }

            //Add filter expression of datasource
            if (Filter.Length > 0)
            {
                string FinalFilter = Filter.Remove(Filter.Length - 4, 3);
                SqlDataSourceSTUDENT_WORKING_TIME.FilterExpression = FinalFilter;
            }
            else
            {
                Gv_STUDENT_WORKING_TIME.DataBind();
            }
        }