private void CourseBottun_Click(object sender, EventArgs e)
{
this.Hide();
LevSearchEmailByCourse f = new LevSearchEmailByCourse(c, l);
f.ShowDialog(this);
}
private void LecSearchStudent_sEmail_FormClosed(object sender, FormClosedEventArgs e)
{
this.Close();
LevSearchEmailByCourse f = (LevSearchEmailByCourse)this.Owner;
f.Show();
}