Gridview1 > Gridview2 > Detailsview1: How to cause a GV2 control DV1

I have 3 controls
Gridview1 onselect update Gridview2, Gridview2 onselect update Detailview1 using Datakeynames of GVs.
ie it looks like
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GV1 [Select] XXX       [Select] XXX GV2 [Select] XXX       [Select] XXX DV1 XXXX XXXX XXXX
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It is working fine except now if another item is selected in GV1, only GV2 is updated but not DV1.
I want when another item of GV1 is selected, then GV2 first item is selected and AT THE SAME TIME DV1 is also changed.
I use this code but D1 does not change:-
GV2.SelectedIndex=0 DV1SqlDatasource.Databind() DV1.Databind()
It seems although I can make G2's first item be selected ON THE FACE of the web page,
It does not get the DataKeyName behind.
What is the code to make sure G2 first item's datakeyname is selected ?
Thanks