public void Update(string id, Event anObject)
        {
            using (var context = new EventContext())
            {
                var newList = new List <MarketingMaterial>();
                var ninja   = context.Events.Include(n => n.Materials)
                              .FirstOrDefault(n => n.id == id);

                if (anObject.Materials.Count < ninja.Materials.Count)
                {
                    // deleted marketing material

                    var differenceQuery =
                        ninja.Materials.Except(anObject.Materials);
                    context.Material.Remove(differenceQuery.FirstOrDefault());
                    context.SaveChanges();
                }
                else
                {
                    // added marketing material
                    var differenceQuery =
                        ninja.Materials.Except(anObject.Materials);

                    var marketingMaterials = differenceQuery as MarketingMaterial[] ?? differenceQuery.ToArray();
                    if (marketingMaterials.Count() != 0)
                    {
                        context.Material.Remove(marketingMaterials.FirstOrDefault());
                    }
                    var differenceQuery1 =
                        anObject.Materials.Except(ninja.Materials);

                    foreach (var material in differenceQuery1)
                    {
                        ninja.Materials.Add(MarketingMaterial.Copy(material));
                    }
                    //   ninja.Materials = newList;
                    ninja.EventLocation        = anObject.EventLocation;
                    ninja.EventType            = anObject.EventType;
                    ninja.EventDate            = anObject.EventDate;
                    ninja.EventName            = anObject.EventName;
                    ninja.EventAttendance      = anObject.EventAttendance;
                    context.Entry(ninja).State = EntityState.Modified;
                    context.SaveChanges();
                }
            }
        }