public SampleItem Update(int id, SampleItem instance)
 {
     // Update the given instance of SampleItem in the collection
     SampleItem item;
     if (Database.Items.TryGetValue(id, out item))
     {
         item.StringValue = instance.StringValue;
     }
     return instance;
 }
 public SampleItem Create(SampleItem instance)
 {
     // Add the new instance of SampleItem to the collection
     Database.Items.Add(instance.Id, instance);
     return Database.Items[instance.Id];
 }