NHibernate is mature ORM. This presentation goes through main concepts of it. Was used at Lviv .NET User Group.

1. NHibernate by Andriy Buday

2. Outline Q1: What is NHibernate? Q2: Why do I need it? Q3: How does it look like? Concepts DEMO 1: Hello World! Q4: How can I proceed with it? Queries More about mapping, querying, usage patterns DEMO 2: Customer-Orders-Products http://andriybuday.blogspot.com/ Let see… will we get what we want!

3. Q1: What is NHibernate?NHibernate is… ORM New level of Abstraction http://andriybuday.blogspot.com/ Paradigm mismatch

4. Q2: Why Do I need it?Because… http://andriybuday.blogspot.com/ Development speed increases Reducing database work Optimizes access to DB, so could even perform better than plain ADO.NET You think in terms of business model, not database More time for real programming

5. Q2: Why Do I need it?Why do I like NHibernate? http://andriybuday.blogspot.com/ Mature Free & Open Source Good community support Flexible Allows you do Domain Driven Design You asked for comparison with other ORM… LINQ to SQL doesn’t really lead you to good models Entity Framework has better Linq and it is Microsoft Visit http://ormbattle.net/ for performance numbers Google.Search(string.Format“Nhibernate vs. {0}”, yourORM);

6. Q3: How does it look like?Concepts: Unit of Work http://andriybuday.blogspot.com/ Kind of “workspace” within which you can do anything you want A Unit Of Work either success or fails as a unit Conceptually like database transactions In NHibernate we have ISession which does the same Conceptually we have the same for in ADO.NET as DataSet

7. Q3: How does it look like?Concepts: ISession http://andriybuday.blogspot.com/ Open a session We get it from the session factory We do some work Session.Add(…) Session.Delete(…) Commit the session Session.Flush(…)

8. Q3: How does it look like?Concepts: ISessionFactory http://andriybuday.blogspot.com/ We are getting our session through this class Very expensive to create One per database or application

9. Q3: How does it look like?Concepts: Summary http://andriybuday.blogspot.com/ Configuration Class builds Session Factory Session Factory builds Session Session is used as Unit Of Work to interaction with objects and persist to underlying database var sessionFactory = newConfiguration().Configure().BuildSessionFactory(); using (var session = sessionFactory.OpenSession()) { var customer = newCustomer(); session.SaveOrUpdate(customer); session.Flush(); }

10. Q3: How does it look like?Architecture: and look from inside? http://andriybuday.blogspot.com/

11. Q3: How does it look like?DEMO: Hello World! http://andriybuday.blogspot.com/ Just basics… to refresh our minds 

12. Q4: How can I proceed with it? More on Query API http://andriybuday.blogspot.com/ Criteria API Object oriented querying ICriteria chaining Easy to write Hard to read HQL API String based Parameterized Similar to SQL Speak in terms of Objects More flexible “from Customer c where c.FirstName = :firstName” session.CreateCriteria(typeof(Customer)) .Add(Restrictions.Eq("FirstName", "Hello"))

13. Q4: How can I proceed with it? Mapping http://andriybuday.blogspot.com/ <hibernate-mappingxmlns="urn:nhibernate-mapping-2.2"default-lazy="true"assembly="LearningNHibernate"namespace="LearningNHibernate"> <classname="Customer"table="Customer"xmlns="urn:nhibernate-mapping-2.2"> <idname="CustomerId"column="CustomerId"type="Int32"> <generatorclass="identity" /> </id> <propertyname="FirstName"column="Firstname"length="50"type="String"> <columnname="Firstname" /> </property> <propertyname="LastName"column="Lastname"length="50"type="String"> <columnname="Lastname" /> </property> </class> </hibernate-mapping> publicclassCustomerMap : ClassMap<Customer> { public CustomerMap() { WithTable("Customer"); Id(x => x.CustomerId); Map(x => x.FirstName, "Firstname"); Map(x => x.LastName, "Lastname").WithLengthOf(50); } }

14. Q4: How can I proceed with it? Fetch strategies http://andriybuday.blogspot.com/ Lazy loading Default for all collections Members are loaded from database when assessed Usually good for performance Session has to stay OPEN Eager Fetching Use when you sure you’ll use data OUTER joins

15. Q4: How can I proceed with it? Caching, batching, concurrency http://andriybuday.blogspot.com/ First level cache Following will run only one SELECT Second level cache Within two sessions you still run one SELECT It is needed to explicitly turn it on everywhere Batch processing <property name="adonet.batch_size">250</property> Concurrency <version name="Version" column="Version"/> var customer1 = session.Get<Customer>(5); var customer2 = session.Get<Customer>(5);

16. Q4: How can I proceed with it? http://andriybuday.blogspot.com/ Use FluentNhibernate to do not bore developers with XML Create wrappers to have NHibernateRepository Implement UnitOfWork VS projects Two ways for kick-off From database to Objects From objects to Database

17. DEMO 2: Mapping, Querying, LazyLoad, etc.. http://andriybuday.blogspot.com/ Damn it! Let’s write some code again!

18. Read blog! Follow me! Visit LVIV .NET UG! http://andriybuday.blogspot.com/ http://andriybuday.blogspot.com/ @andriybuday andriybuday@gmail.com http://dotnetug-lviv.blogspot.com/

19. Links http://andriybuday.blogspot.com/ My blog: http://andriybuday.blogspot.com Lviv .NET User Group: http://dotnetug-lviv.blogspot.com/ NHibernate: Home Page: http://nhibernate.com/ Reference: http://www.nhforge.org/doc/nh/en/index.html Great series of screencasts on NHibernate: http://www.summerofnhibernate.com/ ORM with NHibernate screen cast (2 hours) http://www.flux88.com/uploads/ORMWithNHibernateScreenCast.wmv Tools: Profiler: http://nhprof.com/ Fluent NHibernate: http://fluentnhibernate.org/ MyGeneration: http://www.mygenerationsoftware.com/