the problem is in this line..
cmd = new SqlCommand("FETCHPERSONS_AMT", gn.cn());
to solve it accurately i need to see your connection code above gn.cnopen().Usually i write it in this way..
SqlCommand cmd = new SqlCommand(myQuery, con);
cmd.Connection = con;
where myQuery is the query string and con is SqlConnection.
So if FETCHPERSONS_AMT is your query sting,then use it as..
cmd = new SqlCommand(FETCHPERSONS_AMT, gn.cn());
If it isn't your problem,then see gn.cn() is ok or not..