Your requirements are too incomplete to understand what you need. My best guess is that your requirement is to be able to create a Product and select several Items that you add to that Product. If the Product is a fruit bowl, the Items could be a basket, two apples, three bananas, and a pineapple.
In that case this is a possible domain model:
To add an x amount of items to the product, create a page with a Product-dataview, containing a datagrid of associated Items. Next to the dataview you show a list of Itemtypes which you can select to add it to the list of Items.
If this is not your requirement then please extend the description of your requirements in your question. Anyway, good luck!
given your requirements the domain model is correct.
but I don’t have a clue what the added value is of the dropdown for ItemTable. for me it doesn’t make any sense.