can i use empty resultset object for checking condition

Hi,
I have one query.
Can we use empty resultset objetct for checking any condition.
supose in my query:
rs= st.ExecuteQuery("select * from user where userid=1 and eventid =4");
which result in empty resultset . so can i use rs for following use as:
if(rs==null){
do some operation
}else{
do another operation
}
Any suggestion is highly appreciated.
Thanks and Regards
Haresh