Validating a DropDownlist in a Grid View

hi,
first what do mean by validation here? if you just want to get its value then use jquery syntax like

$(document).ready(function() {
    $("YourDroDownListID").change(function () {
             alert($("YourDroDownListID option:selected").text());
             //do more logic here
        });
});

and now you can make your required logic here.
good luck.