Immutable entities

An immutable entity is an entity that never changes once it has been created. An example could be entries in event log. New log entries may be added all the time; however, once saved, they are not supposed to be modified.

This behavior could of course be enforced in code, or perhaps even in the database, but if we tell NHibernate to treat specific classes as immutable, we can both enforce the immutability and allow NHibernate optimize performance a bit.

Getting ready

Complete the Getting ready instructions at the beginning of this chapter.

How to do it…

1. Add a new folder named ImmutableEntities to the MappingRecipes project.

2. Add a new class named LogEntry to the folder:

   using System;
   
   namespace MappingRecipes.ImmutableEntities
   {
     public class LogEntry
     {
       public virtual Guid Id { get; protected set; }
       public virtual string Message { get; set; }
     }
   }

3. Add a new embedded mapping named LogEntry.hbm.xml to the folder:

   <?xml version="1.0" encoding="utf-8" ?>
   <hibernate...