problem of dropdownlist in gridview

when editing the grid view 
1.i have one dropdownlist like product type
product type items are liquids, tablets
2.i have another dropdownlist like batch code 
batch code items are 
for tablets  batch code items vzx,vdz
and liquids  batch code items FTN,VXX
my problem is before  edit button click 
i have 
product type tablets and batch  code is vzx 
after clickin edit button click also the dropdown should same 
if user can may change the or not but it set default values 
in grid view 
its urgent 
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