modelbinding to custom ui class which contains a list of other custom ui class

Question

Hi, I have a custom class UIPerson, which contains a listItemsForSale()

Each UIItem has an int field QuantityAvailable.

In my view for Create Person, I have

foreach(var i in Model.ItemsForSale)
{
    <%=Html.EditorFor(x => item.QuantityAvailable) &>
}

this correctly displays a textbox with '1', the default value, but when I change these values, they are not posted properly. Properties directly on the UIPerson are posted correctly.

Is there anything else I need to add in order for this to work? thank you.