NHibernate QueryOver Subjective Where?

Question

So in SQL I can write a query like this:

SELECT
  A,
  B,
  C
FROM
  myTABLE
WHERE
  (@X is NULL OR A = @X) AND
  (@Y is NULL OR B = @Y) AND
  (@Z is NULL OR C = @Z)

in order create a single query that returns all entries if no filtering parameters are specified, or a subset if any of them are specified. But how would I go about doing this using Nhibernate's QueryOver? I'm not even fully sure how to do an OR with QueryOvery at all...

Answer 1

In order to subjectively query (based on the parameter), the accepted method would be to build the where clause in pieces as such:

var qry = session.QueryOver<obj>(); 
if (!String.IsNullOrEmpty(A)) { qry.Where(x => x.a == A); } 
if (!String.IsNullOrEmpty(B)) { qry.Where(x => x.b == B); } 
if (!String.IsNullOrEmpty(C)) { qry.Where(x => x.c == C); } 
List<obj> data = qry.List<obj>().ToList();

So that the final result is the exact query to run for a given set of parameters, rather the generalized SQL query specified in the original post.