public Series Update(Series series)
 {
     var sers = _context.Series.FirstOrDefault(cp => cp.Id == series.Id);
     if (sers == null) throw new ArgumentException();
     _context.Entry(series).State = System.Data.Entity.EntityState.Modified;
     _context.SaveChanges();
     return sers;
 }
 public Series Delete(Series series)
 {
     var sers = _context.Series.Remove(series);
     _context.SaveChanges();
     return sers;
 }
 public Series Create(Series series)
 {
     var sers = _context.Series.Add(series);
     _context.SaveChanges();
     return sers;
 }