You can use FeatureDataGrid.SelectionChanged event and iterate through e.AddedItems. To convert row to graphic, you can use the following method (add using System.Reflection).
private void MyDataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
foreach (var item in e.AddedItems)
{
var g = GetGraphicSibling(item);
}
}
private static Graphic GetGraphicSibling(object item)
{
if (item != null)
{
MethodInfo mi = item.GetType().GetMethod("GetGraphicSibling");
if (mi != null)
return mi.Invoke(item, null) as Graphic;
}
return null;
}