Hi,

Dealing with the Visual Studio form designer and collection like this is extremely tricky. VS does not recognize when items in a collection change in a case like this where you have derived classes. It doesn't track the item that was edited and the new item you added are the same thing.

So basically, what happens here is that when you open up the collection editor and change the existing items and save, it clears the whole collection and adds the items into a new list. Then, when you run the app, a new OptionSet is created and DotNet deserializes the three items.

The OptionSet control probably uses a TypeConverter and/or a UITypeEditor on the Items property in order to deal with this. So you might be able to use the same one.

You might also be able to get around this by playing around with implementing ISupportInitialize or maybe overriding OnCreateControl to remove the default items. But this will take a lot of trial-and-error to find the right way to get it to work, if it's even possible.

My advice would be to create your own collection of items and then create the optionset items base on your own items. But personally, it's probably not worth the effort it will take to get it working the way you want it - in my experience.