Using session.Merge

Session.Merge is perhaps one of the most misunderstood features in NHibernate. In this recipe, we'll show you how to use session.Merge to associate a dirty, detached entity with a new session. This is particularly handy when recovering from StaleObjectStateExceptions.

Getting ready

Follow the Getting ready step in the Save entities to the database recipe in this chapter.

How to do it…

1. Add a new folder named MergingEntities to the SessionRecipes project.

2. Add a class named Recipe to the folder:

   using System;
   using NH4CookbookHelpers.Queries;
   using NH4CookbookHelpers.Queries.Model;
   using NHibernate;
   
   namespace SessionRecipes.MergingEntities
   {
     public class Recipe : QueryRecipe
     {
       protected override void Run(ISessionFactory sessionFactory)
       {
         var book = CreateAndSaveBook(sessionFactory);
         book.Name = "Dormice in Action";
         book.Description = "Hibernation of the Hazel Dormouse";
         book.UnitPrice = 0.83M;
         book.ISBN = "0123";
   
         using (var session...