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How can I have NHibernate only generate the SQL without executing it?

You can get the generated sql queries without execution with the following methods: For the NHibernate.Linq queries: public String GetGeneratedSql(System.Linq.IQueryable queryable, ISession session) { var sessionImp = (ISessionImplementor) session; var nhLinqExpression = new NhLinqExpression(queryable.Expression, sessionImp.Factory); var translatorFactory = new ASTQueryTranslatorFactory(); var translators = translatorFactory.CreateQueryTranslators(nhLinqExpression, null, false, sessionImp.EnabledFilters, sessionImp.Factory); return translators[0].SQLString; } For Criteria queries: public … Read more

How can you do paging with NHibernate?

ICriteria has a SetFirstResult(int i) method, which indicates the index of the first item that you wish to get (basically the first data row in your page). It also has a SetMaxResults(int i) method, which indicates the number of rows you wish to get (i.e., your page size). For example, this criteria object gets the … Read more

Persist Data by Programming Against Interface

Your repository should accept BankAccount – not IBankAccount because Linq-to-sql doesn’t know what is IBankAccount and compiler doesn’t allow you to store it without casting it first to BankAccount (that can obviously fail at runtime if IBankAccount instance is not a BankAccount). Once you have BankAccount you simply call: Context.BankAccounts.Add(account); Context.SubmitChanges();

Minimal and correct way to map one-to-many with NHibernate

Just few hints, summarizing the most suitable standards I found out when working with NHibernate. 1) If there is a bi-directional reference in persitence (DB column), express it in C# code bi-directional as well. Other words, if a child has reference to parent, parent should have reference to child. public class Employee { … public … Read more

What’s the difference between session.Merge and session.SaveOrUpdate?

This is from section 10.7. Automatic state detection of the Hibernate Reference Documentation: saveOrUpdate() does the following: if the object is already persistent in this session, do nothing if another object associated with the session has the same identifier, throw an exception if the object has no identifier property, save() it if the object’s identifier … Read more

many-to-many with extra columns nhibernate

The many-to-many, without the explicit mapping of the pairing table as an entity – is in NHibernate of course suported. So, in case, that the Date column is autogenerated, or nullable (does not have to be inserted by app/NHiberante), we can do it like here: 6.8. Bidirectional Associations <class name=”User”> <id name=”Id” column=”Uid”/> … <bag … Read more

Fighting cartesian product (x-join) when using NHibernate 3.0.0

Ok, I wrote an example for myself reflecting your structure and this should work: int projectId = 1; // replace that with the id you want // required for the joins in QueryOver Project pAlias = null; Partner paAlias = null; PartnerCosts pcAlias = null; Address aAlias = null; Money mAlias = null; // Query … Read more

NHibernate QueryOver with Fetch resulting multiple sql queries and db hits

I would say, that this behaviour is what we should expect. Let’s have a scenario, in which we have in the system 2 users and 2 roles User1 – Role1 // has only Role1 User2 – Role1 // now we see that Role2 has more then User1 User2 – Role2 Let’s say, that the first … Read more

Criteria.DISTINCT_ROOT_ENTITY vs Projections.distinct

While similar names, the usage is different. I. Projections.distinct(Projections.property(“id”)); this statement would be translated into SQL Statement. It will be passed to DB Engine and executed as a SQL DISTINCT. See: 17.9. Projections, aggregation and grouping so e.g. this example: List results = session.createCriteria(Cat.class) .setProjection( Projections.projectionList() .add( Projections.distinct(Projections.property(“id”)) ) ) .list(); would seems like: SELECT … Read more

Inverse Attribute in NHibernate

The inverse attribute must not be set to true … You use the inverse attribute to specify the ‘owner’ of the association. (An association can have only one owner, so one end has to be set to inverse, the other has to be set to ‘non inverse’). (Owner: inverse=false; Non-owner: inverse=true) In a one-to-many association, … Read more