Update command in Fluent NHibernate - nhibernate

Question

I am trying to update an object after retrieving it from a database.
This fires 2 queries , one for the select and the other for the update, is there any way of update an object using Fluent NHiberNate firing only one query ?
My code is as below:
var userProfile = userProfileRepository
.Find(x => x.ClientId == clientId)
.FirstOrDefault();
/* update UserProfile object here */
userProfileRepository.SaveOrUpdate(userProfile);
the SaveOrUpdate Method looks as such :
public bool SaveOrUpdate(T instance)
{
using (var session = SessionManager.OpenSession())
{
using (var transaction = session.BeginTransaction())
{
session.SaveOrUpdate(instance);
transaction.Commit();
}
return true;
}
}

Answer 1

In case that your issue is:
regardless of what I do, SaveOrUpdate() always sends SELECT then UPDATE
You should check the doc:
5.1.4.7. Assigned Identifiers
If you want the application to assign identifiers (as opposed to having NHibernate generate them), you may use the assigned generator. This special generator will use the identifier value already assigned to the object's identifier property. Be very careful when using this feature to assign keys with business meaning (almost always a terrible design decision).
Due to its inherent nature, entities that use this generator cannot be saved via the ISession's SaveOrUpdate() method. Instead you have to explicitly specify to NHibernate if the object should be saved or updated by calling either the Save() or Update() method of the ISession.
So, if your Fluent configuration sets the ID to be assigned - NHibernate has no other way then check if it
exists
or is new
because used method was SaveOrUpdate()
Solution(s)
1) Change the ID to be generated by DB or NHiberante 2) use explicit Update()

Answer 2

Are you trying to create an
UPDATE ... WHERE ...
statement?
AFAIK the NHibernate way to do this, is to select the appropriate objects (using the WHERE clause), update the fields, and persist them again.
var tempObjects = _session.Query<myObject>.Where(o => o.Id > 500);
// update proxy objects
foreach (var o in tempObjects)
{
o.MyValue = updatedValue;
}
// commit updated objects
_session.Update(tempObjects);
To be honest, we've used ISession.CreateSQLQuery ourselves. I hate using SQL in code because it breaks in refactoring, but if you must - here's how:
_session.CreateSQLQuery(
#"UPDATE [MyTable] SET [MyValue]=:updatedvalue WHERE Id > 500")
.SetParameter("updatedvalue", updatedValue)
.ExecuteUpdate();