Of all the ASP.NET MVC books out there Steve Sanderson’s Pro ASP.NET MVC Framework is, in my opinion, probably one of the best. The author’s writing style and explanations are excellent. He covers MVC 1.0 in great detail and although I generally hate exclusive case study books this book devotes 3 of it’s 15 chapters to looking at developing a small shopping cart application. Steve introduces quite a few good pratices such as recognised design patterns eg Repository Pattern, Inversion of Control (IOC)/Dependency Injection (DI) and the use of mocking tools (namely Moq). He approaches the development from both a Domain Driven Design (DDD) and Test Driven Development (TDD) perspective although, as he stresses, you are not obliged to follow the testing style if it doesn’t suit you.

Anyway getting to the point of this post: SportsStore uses IOC to loosely couple the components of the application, this allows for easier testing and the ability to swap out dependencies. SportsStore uses the popular Castle Windsor container to facilitate IOC. In doing so the application is able to easily use any data persistence technology it chooses. Steve chose to use LinqToSql as the data persistence choice but I’m not that keen on it as it introduces a slight ‘dusting’ on the application’s domain model entities (and ties it to SQL Server). I like my business objects to be clean and free from any attributes. One of NHibernate’s nice features is it’s persistence ignorance. It leaves your domain entities clean, they dont have to implement any special interface or have any attributes applied to them.

So with all that said let’s quickly add NHibernate support to SportStore:

1. Download the latest NHibernate binaries here
2. In SportsStore’s DomianModel project create a new root folder called NHibernateBinaries and put the NHibernate.dll in there.
3. Add a reference to the NHibernate.dll
4. In the Entities folder create a NHibernate mapping file for the products entity:
   It should look like this:

   <?xml version="1.0" encoding="utf-8" ?>
   <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
    <class name="DomainModel.Entities.Product, DomainModel" table="Products">
    <id name="ProductID" type="Int32" unsaved-value="null">
    <column name="ProductID" length="16" sql-type="int" not-null="true" unique="true" index="PK_Product"/>
    <generator />
    </id>
    <property name="Name" type="String">
    <column name="Name" length="100" sql-type="nvarchar" not-null="true"/>
    </property>
    <property name="Description" type="String">
    <column name="Description" length="500" sql-type="nvarchar" not-null="true"/>
    </property>
    <property name="Price" type="Decimal">
    <column name="Price" length="16" sql-type="decimal" not-null="false"/>
    </property>
    <property name="Category" type="String">
    <column name="Category" length="50" sql-type="nvarchar" not-null="true"/>
    </property>
    </class>
   </hibernate-mapping>
   

   name this file Product.hbm.xml

5. In the Concrete folder of SportsStore Add this class NHibernateSessionManager.cs

   using System;
   using System.Collections.Generic;
   using System.Configuration;
   using System.Runtime.Remoting.Messaging;
   using System.Text;
   using NHibernate;
   using NHibernate.Cache;
   using System.Web;
   using System.Data;
   
   namespace DomainModel.Concrete
   {
       /// <summary>
       /// Handles creation and management of sessions and transactions.  It is a singleton because
       /// building the initial session factory is very expensive. Inspiration for this class came
       /// from Chapter 8 of Hibernate in Action by Bauer and King.  Although it is a sealed singleton
       /// you can use TypeMock (http://www.typemock.com) for more flexible testing.
       /// </summary>
       public sealed class NHibernateSessionManager
       {
           #region Thread-safe, lazy Singleton
   
           /// <summary>
           /// This is a thread-safe, lazy singleton.  See http://www.yoda.arachsys.com/csharp/singleton.html
           /// for more details about its implementation.
           /// </summary>
           public static NHibernateSessionManager Instance
           {
               get
               {
                   return Nested.nHibernateSessionManager;
               }
           }
   
           /// <summary>
           /// Initializes the NHibernate session factory upon instantiation.
           /// </summary>
           private NHibernateSessionManager()
           {
               InitSessionFactory();
           }
   
           /// <summary>
           /// Assists with ensuring thread-safe, lazy singleton
           /// </summary>
           private class Nested
           {
               static Nested() { }
               internal static readonly NHibernateSessionManager nHibernateSessionManager = new NHibernateSessionManager();
           }
   
           #endregion
   
           private void InitSessionFactory()
           {
               NHibernate.Cfg.Configuration cfg = new NHibernate.Cfg.Configuration();
   
               // The following makes sure the the web.config contains a declaration for the HBM_ASSEMBLY appSetting
               if (ConfigurationManager.AppSettings["HBM_ASSEMBLY"] == null ||
                   ConfigurationManager.AppSettings["HBM_ASSEMBLY"] == "")
               {
                   throw new ConfigurationErrorsException("NHibernateManager.InitSessionFactory: \"HBM_ASSEMBLY\" must be " +
                       "provided as an appSetting within your config file. \"HBM_ASSEMBLY\" informs NHibernate which assembly " +
                       "contains the HBM files. It is assumed that the HBM files are embedded resources. An example config " +
                       "declaration is <add key=\"HBM_ASSEMBLY\" value=\"MyProject.Core\" />");
               }
   
               cfg.AddAssembly(System.Configuration.ConfigurationManager.AppSettings["HBM_ASSEMBLY"]);
               sessionFactory = cfg.BuildSessionFactory();
           }
   
           /// <summary>
           /// Allows you to register an interceptor on a new session.  This may not be called if there is already
           /// an open session attached to the HttpContext.  If you have an interceptor to be used, modify
           /// the HttpModule to call this before calling BeginTransaction().
           /// </summary>
           public void RegisterInterceptor(IInterceptor interceptor)
           {
               ISession session = threadSession;
   
               if (session != null && session.IsOpen)
               {
                   throw new CacheException("You cannot register an interceptor once a session has already been opened");
               }
   
               GetSession(interceptor);
           }
   
           public ISession GetSession()
           {
               return GetSession(null);
           }
   
           /// <summary>
           /// Gets a session with or without an interceptor.  This method is not called directly; instead,
           /// it gets invoked from other public methods.
           /// </summary>
           private ISession GetSession(IInterceptor interceptor)
           {
               ISession session = threadSession;
   
               if (session == null)
               {
                   if (interceptor != null)
                   {
                       session = sessionFactory.OpenSession(interceptor);
                   }
                   else
                   {
                       session = sessionFactory.OpenSession();
                   }
   
                   threadSession = session;
               }
   
               return session;
           }
   
           public void CloseSession()
           {
               ISession session = threadSession;
               threadSession = null;
   
               if (session != null && session.IsOpen)
               {
                   session.Close();
               }
           }
   
           public void BeginTransaction(IsolationLevel il)
           {
               ITransaction transaction = threadTransaction;
   
               if (transaction == null)
               {
                   transaction = GetSession().BeginTransaction(il);
                   threadTransaction = transaction;
               }
           }
   
           public void CommitTransaction()
           {
               ITransaction transaction = threadTransaction;
   
               try
               {
                   if (transaction != null && !transaction.WasCommitted && !transaction.WasRolledBack)
                   {
                       transaction.Commit();
                       threadTransaction = null;
                   }
               }
               catch (HibernateException ex)
               {
                   RollbackTransaction();
                   throw ex;
               }
           }
   
           public void RollbackTransaction()
           {
               ITransaction transaction = threadTransaction;
   
               try
               {
                   threadTransaction = null;
   
                   if (transaction != null && !transaction.WasCommitted && !transaction.WasRolledBack)
                   {
                       transaction.Rollback();
                   }
               }
               catch (HibernateException ex)
               {
                   throw ex;
               }
               finally
               {
                   CloseSession();
               }
           }
   
           private ITransaction threadTransaction
           {
               get
               {
                   return (ITransaction)CallContext.GetData("THREAD_TRANSACTION");
               }
               set
               {
                   CallContext.SetData("THREAD_TRANSACTION", value);
               }
           }
   
           private ISession threadSession
           {
               get
               {
                   return (ISession)CallContext.GetData("THREAD_SESSION");
               }
               set
               {
                   CallContext.SetData("THREAD_SESSION", value);
               }
           }
   
           private ISessionFactory sessionFactory;
       }
   }
   

   also add a new NHibernateProductsRespository.cs class

   using System;
   using System.Collections.Generic;
   using System.Linq;
   using System.Data.Linq;
   using System.Text;
   using DomainModel.Abstract;
   using DomainModel.Entities;
   using NHibernate;
   using NHibernate.Expression;
   
   namespace DomainModel.Concrete {
   
       public class NHibernateProductsRepository : IProductsRepository {
   
           private static IList<Product> GetProducts() {
               ISession isess = NHibernateSessionManager.Instance.GetSession();
               return isess.CreateCriteria(typeof(Product))
                   .AddOrder(Order.Asc("Name"))
                   .List<Product>();
           }
   
           public IQueryable<Product> Products {
               get { return GetProducts().AsQueryable(); }
           }
   
       }
   }
   

6. Finally modify your web.config to add the NHibernate sections

   <configSections>
   <section name="castle"
   type="Castle.Windsor.Configuration.AppDomain.CastleSectionHandler,
   Castle.Windsor" />
   <section name="nhibernate"
   type="System.Configuration.NameValueSectionHandler, System,
   Version=1.0.5000.0, Culture=neutral,
   PublicKeyToken=b77a5c561934e089"/>
   </configSections>
   
   <nhibernate>
   <add
    key="hibernate.connection.provider"
   value="NHibernate.Connection.DriverConnectionProvider"/>
   <add
   key="hibernate.dialect" value="NHibernate.Dialect.MsSql2000Dialect"/>
   <add
    key="hibernate.connection.driver_class"
   value="NHibernate.Driver.SqlClientDriver"/>
   <add
   key="hibernate.connection.connection_string" value="Data Source =
   yourserver;Initial Catalog = SportsStore;user
   id=sa;password=yourpassword;"/>
   </nhibernate>
   
   <appSettings>
   <add
    key="HBM_ASSEMBLY" value="DomainModel"/>
   </appSettings>

Compile the solution and now you are free to change your implementation of Products repository to the NHibernateProductsRespository by altering the castle component in your web.config: