private void dt_teacher_SelectionChanged(object sender, EventArgs e)
{
if (dt_teacher.SelectedRows.Count > 0)
{
btnAdd_teacher.Visible = false;
DataGridViewRow row = dt_teacher.SelectedRows[0];
Teacher_User_Account = row.Cells[0].Value.ToString();
txtUserName_teacher.Text = row.Cells[0].Value.ToString();
txtCMND_TCC_teacher.Text = row.Cells[5].Value.ToString();
txtFull_name_teacher.Text = row.Cells[4].Value.ToString();
txtMail_teacher.Text = row.Cells[8].Value.ToString();
txtSDT_teacher.Text = row.Cells[7].Value.ToString();
dtTeacher_Picker.Value = DateTime.Parse(row.Cells[6].Value.ToString());
Grade_CBB.Text = BUS_Admin.findGradeByID(row.Cells[2].Value.ToString());
}
}