/// <summary>
/// Delete Section And ALL Its Children
/// </summary>
/// <param name="id"></param>
/// <returns>1)section, when deletes all succesfully 2) null, when failed to delete section or one of its children</returns>
public Section DeleteSectionAndChildren(string id)
{
var section = Sections.Include(c => c.Lessons).FirstOrDefault(c => c.Id == id);
if (section != null)
{
Lessons.RemoveRange(section.Lessons);
Sections.Remove(section);
return(section);
}
return(null);
}
