_SelectionChanged event doesn't recognize data with null fields

[JAck90]

I'm having some problems with the _SelectionChanged event on an ASPX grid view using devexpress v9.3. The ASPX Gridview that is on the page doesn't recognize rows where some cells have no value. I can select rows where all of the cells have been populated and the keyFieldName is returned, however if some of the rows have no data it wont return anything.I know each row has been assigned data for the KeyFieldName as I have outputted this to the grid. Can anyone help me please x