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Model View Presenter with ASP.NET

, 16 Oct 2007 1.1M 24.6K 596
This article describes using the Model-View-Presenter pattern within ASP.NET 2.0 to encourage proper separation of concerns between presentation and business logic
amosttrivialexample.zip
AMostTrivialExample
App_Code
Solution Items
nunit.framework.dll
enterpriseapplicationmvp.zip
EnterpriseApplicationMvp
MvpSample.Core
bin
Debug
Castle.DynamicProxy.dll
Iesi.Collections.dll
log4net.dll
MvpSample.Core.dll
MvpSample.Core.pdb
NHibernate.dll
NHibernate.Generics.dll
DataInterfaces
Domain
Properties
MvpSample.Data
bin
Debug
Castle.DynamicProxy.dll
Iesi.Collections.dll
log4net.dll
MvpSample.Core.dll
MvpSample.Core.pdb
MvpSample.Data.dll
MvpSample.Data.pdb
NHibernate.dll
NHibernate.Generics.dll
Properties
MvpSample.Presenters
bin
Debug
Castle.DynamicProxy.dll
Iesi.Collections.dll
log4net.dll
MvpSample.Core.dll
MvpSample.Core.pdb
MvpSample.Presenters.dll
MvpSample.Presenters.pdb
NHibernate.dll
NHibernate.Generics.dll
Properties
ViewInterfaces
MvpSample.Tests
bin
Debug
Castle.DynamicProxy.dll
Iesi.Collections.dll
log4net.dll
MvpSample.Core.dll
MvpSample.Core.pdb
MvpSample.Data.dll
MvpSample.Data.pdb
MvpSample.Presenters.dll
MvpSample.Presenters.pdb
MvpSample.Tests.dll
MvpSample.Tests.pdb
NHibernate.dll
NHibernate.Generics.dll
Data
Domain
MockDao
Presenters
Properties
MvpSample.Web
App_Code
Bin
Castle.DynamicProxy.dll
Castle.MicroKernel.dll
Castle.MicroKernel.dll.refresh
Castle.Model.dll
Castle.Model.dll.refresh
Castle.Windsor.dll
Castle.Windsor.dll.refresh
Iesi.Collections.dll
Iesi.Collections.dll.refresh
log4net.dll
log4net.dll.refresh
MvpSample.Core.dll
MvpSample.Core.pdb
MvpSample.Data.dll
MvpSample.Data.pdb
MvpSample.Presenters.dll
MvpSample.Presenters.pdb
NHibernate.dll
NHibernate.Generics.dll
Config
Global.asax
Views
Solution Items
Castle.MicroKernel.dll
Castle.Model.dll
Castle.Windsor.dll
Iesi.Collections.dll
log4net.dll
NHibernate.dll
NHibernate.Generics.dll
nunit.framework.dll
eventhandlingmvp.zip
EventHandlingMvp
App_Code
Solution Items
nunit.framework.dll
Views
using System.Configuration;
using System.Runtime.Remoting.Messaging;
using NHibernate;
using NHibernate.Cache;
using Configuration=NHibernate.Cfg.Configuration;

namespace MvpSample.Data
{
    /// <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() {
            Configuration cfg = new 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(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() {
            ITransaction transaction = threadTransaction;

            if (transaction == null) {
                transaction = GetSession().BeginTransaction();
                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;
    }
}

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About the Author

Billy McCafferty
Web Developer
United States United States
No Biography provided

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