If you have DataKeysNames like
DataKeyNames="targetid,RequestID"
You can access them as
string targetID= gv.DataKeys[e.RowIndex].Values[0].ToString();
string requestID= gv.DataKeys[e.RowIndex].Values[1].ToString();
Or you can use as below as well,
gv.DataKeys[e.SelectedIndex].Values["targetid"];
gv.DataKeys[e.SelectedIndex].Values["RequestID"];
Hope this answers your questions.