in gidview selct only distinct values

Question

How to select distinct values in gridview

i have grid view like this

namr       mobile          area
raju         90165432      hyd
ramu        98493131      hyd
raju         90165432      hyd
jki           98493131      hyd
kasd        90165432      hyd


when i select options all... select only unique mobile numbrs only ..not duplicate mobile numbers

raju 90165432 hyd
ramu 98493131 hyd