使用ASP.Net ListView.ExtractItemValues，如何在ListViewDataItem中的RadioButtonList中获取所选项？

I'm attempting to iterate over the ListViewDataItems in an ASP.Net ListView, and use the ListView.ExtractItemValues to get the values from DataBoundControls. This works fine with ITextControls, but I am having difficulty getting the Selected Item from a RadioButtonList. I'm attempting to iterate over the ListViewData