Custom ILists, ComboBox Prompts

Following up on the last post which showed how to use custom ILists to merge two collections, this post shows how to use a custom IList to concatenate or append two collections.
Such a thing might be useful in a situation where you want to add more than one prompt to a ComboBox. In the example, I have the days of the week to choose from, but also want to add “Every Day”, “Weekdays” and “Weekends” without modifying the original days of the week collection. Of course, if you concatenate the two collections, it offsets your selectedIndex.
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