check box value remain FALSE

hello every body,

I have made Gridview on asp.net that is dynamically filled based on the user link yahoo addressbook or hotmail addressbook, I put a checkbox field to allow ckecking multiple rows and this was my problem that ckeckbox always return false even when you check it it's checked value false.

have any one an idea about what is the problem in that?
how come i have already checked the desired rows but its values still false?
how could i solve this issue?

 

Thanks in advance.. i appreciate any help 
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