I have already find out the solution, i just want to post it so this may be useful for some people
This is the button that use command
You may have made EnableViewState="false" in grid.
EnableViewState="false"
If this is the case, Rowcommand Event will also not fire.
Rowcommand Event
You have made EnableEventValidation="true" on page.
EnableEventValidation="true"
If this is the case, RowCommand Event Will Not Fire, Set This To false.
RowCommand Event
The solution is to set it to true.