private void btn_Submit_Click(object sender, EventArgs e)
{
ProgramData.ReadyToSelectCoursesList.Clear();
for (var i = 0; i < list_Course.Items.Count; i++)
{
ProgramData.ReadyToSelectCoursesList.Add(list_Course.Items[i].Text);
}
FileIo.SaveListToTxt("sel_courses.list", ProgramData.ReadyToSelectCoursesList);
Close();
}