Transaction context

Business object often have the need to enrolled on transaction. In order to implement it, we have the following choices:

1. Pass transaction to every business object;
2. Simply assume a pragmatic one transaction per session.

I'm presently choosing this last one on most of my implementations for simplicity sake. HEre are some of my implementation details:

a) create a session manager:

 /// 

 /// 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.
 /// 
 public sealed class NHibernateSessionManager

b) in the session manager, handle context by session:

     /// 

     /// Since multiple databases may be in use, there may be one transaction per database
     /// persisted at any one time.  The easiest way to store them is via a hashtable
     /// with the key being tied to session factory.  If within a web context, this uses
     ///  instead of the WinForms specific .
     /// Discussion concerning this found at http://forum.springframework.net/showthread.php?t=572
     /// 
     private ITransaction ContextTransaction
     {
         get
         {
             if (IsInWebContext())
             {
                 return (ITransaction)HttpContext.Current.Items[TRANSACTION_KEY];
             }
             else
             {
                 return (ITransaction)CallContext.GetData(TRANSACTION_KEY);
             }
         }
         set
         {
             if (IsInWebContext())
             {
                 HttpContext.Current.Items[TRANSACTION_KEY] = value;
             }
             else
             {
                 CallContext.SetData(TRANSACTION_KEY, value);
             }
         }
     }

c) involve it on a TransactionContext class that derives from IDisposable, making use of NHibernateSessionManager for usage simplicity sake.

 using (TransactionContext transactionContext = new TransactionContext())
 {
  // do some stuff
  transactionContext.SetComplete();
 }

Although this is an NHibernate implementation, the patterns themselves are general to transactions.