5

Managing State and Saving Data

In the previous chapter, the LINQ to NHibernate API was discussed. Like the IQuery, ICriteria, and QueryOver APIs, LINQ to NHibernate provides functionality that enables the retrieval of data from a database in an object-oriented manner. Up to now, only the retrieval of data has been covered. This chapter, however, covers data insertion and entity state management. This is where many of NHibernate's strengths lie. It is also a more complicated aspect of NHibernate, however, and therefore more diffi cult to comprehend and implement. This chapter clarifi es the following topics:

• An overview of concurrency
• Using NHibernate versioning
• Implementing a custom data type using IUserType
• Inserting data into a database