I have a WPF MVVM application. In the View I have a multiselect `ListBox`. In the ViewModel I have a property for the selected items in the List.

Using a technique similar to the one in the answer to [this](https://stackoverflow.com/questions/414074/twoway-manual-binding-implementation-for-listbox-selecteditems) question I can bind my property to the `ListBox`.

But I also want to do data validation via `IDataErrorInfo`. All I want to do is check that the user has selected at least one item in the list. Adding `ValidatesOnDataErrors=True` to the binding doesn't work.

Is there any way to have a multiselect listbox that's databound with IDataErrorInfo?