Book Image

NHibernate 4.x Cookbook - Second Edition

By : Gunnar Liljas, Alexander Zaytsev, Jason Dentler
Book Image

NHibernate 4.x Cookbook - Second Edition

By: Gunnar Liljas, Alexander Zaytsev, Jason Dentler

Overview of this book

NHibernate is a mature, flexible, scalable, and feature-complete open source project for data access. Although it sounds like an easy task to build and maintain database applications, it can be challenging to get beyond the basics and develop applications that meet your needs perfectly. NHibernate allows you to use plain SQL and stored procedures less and keep focus on your application logic instead. Learning the best practices for a NHibernate-based application will help you avoid problems and ensure that your project is a success. The book will take you from the absolute basics of NHibernate through to its most advanced features, showing you how to take full advantage of each concept to quickly create amazing database applications. You will learn several techniques for each of the four core NHibernate tasks—configuration, mapping, session and transaction management, and querying—and which techniques fit best with various types of applications. In short, you will be able to build an application using NHibernate by the end of the book. You will also learn how to best implement enterprise application architecture patterns using NHibernate, leading to clean, easy-to-understand code and increased productivity. In addition to new features, you will learn creative ways to extend the NHibernate core, as well as gaining techniques to work with the NHibernate search, shards, spatial, envers, and validation projects.
Table of Contents (17 chapters)
NHibernate 4.x Cookbook Second Edition
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Updating the database


It's usually required to update your database if mappings for your application have changed. In this recipe, we'll generate a SQL script to update your database objects.

Getting ready

Complete the Configuring NHibernate with App.config or Web.config recipe at the beginning of this chapter.

Note

This recipe works for any RDBMS supported by NHibernate. To use a different system, adjust your connection string and dialect accordingly.

How to do it...

  1. Open Program.cs.

  2. Add these using statements to the beginning of the file:

    using Eg.Core;
    using NHibernate.Mapping.ByCode; 
    using NHibernate.Tool.hbm2ddl;
  3. Modify the Main method to look similar to this:

    var nhConfig = new Configuration().Configure();
    var mapper = new ConventionModelMapper();
    nhConfig.AddMapping(mapper.CompileMappingFor(new[] { typeof(TestClass) }));
    var update = new SchemaUpdate(nhConfig);
    update.Execute(false, true);
    Console.WriteLine("The tables have been updated");
    Console.ReadKey();
  4. Build and run your application. Inspect the table(s) in the database.

  5. Modify TestClass to include an additional property:

    public virtual string Description { get; set; }
  6. Build and run the application again. The TestClass table should now have a new column corresponding to the Description property.

How it works...

Using the mapping metadata from the configuration object and the current dialect, hbm2ddl analyzes the existing structure of your database and generates a script to fulfill the differences. The SchemaUpdate only adds missing objects, and does not try to remove anything.

See also

  • Configuring NHibernate with App.config

  • Configuring NHibernate with hibernate.cfg.xml

  • Configuring NHibernate with code

  • Configuring NHibernate with Fluent NHibernate

  • Generating the database

  • Scripting the database