Table of Contents

• Introduction
• A Brief Discussion on Object-Relational Mappers
• Scenarios
• Decision Points
• Features
• Vendors/Software Authors in this Guide
• Products Profiled in this Guide
• General Criteria
• Feature Tables
• Products Not Profiled in this Guide
• Informed Opinions
• Glossary
• About the Guides

Executive Editor - .NET Developer Series
Mike Gunderloy | http://www.larkware.com

Author
Jason Mauss | http://www.devcampus.com

Copy Editor
Melanie Spiller | http://blogs.officezealot.com/spiller/

Design & Layout
Palo Creative | http://www.palocreative.com

Publisher
Xtras, Inc. | http://www.xtras.com

Introduction

Hello and welcome to the sixth in Xtras' series of How-To-Select™ Guides: How-To-Select an Object-Relational Mapping Tool for .NET.

In this particular Guide, we've evaluated products designed to help you manage that mapping of relational data into objects and vice versa. As with the other Guides in the .NET Developer Guide Series, we've written this Guide for developers using C#, VB.NET, or any other .NET language. We've included a discussion of what obfuscation does and why you might want to use it, and offered guidance to help you choose the most appropriate obfuscation product for your own needs.

The Best Product for your Needs

We bring you the info you need to make informed choices when choosing .NET components and tools for your project. Each How-To-Select Guide goes in-depth into a different product category. We offer expert selection guidance and profile every product we can find in the relevent category, limited only by the vendor's willingness to participate. Plus we'll revise each Guide biannually to keep abreast of changes.

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A Brief Discussion on Object-Relational Mappers

"Progress isn't made by early risers. It's made by lazy men trying to find easier ways to do something." - Robert Heinlein, Time Enough For Love

If there's ever been one thing programmers have been good at since the dawn of computing, it's been figuring out how to make their jobs easier. Once certain patterns emerge, reusable code and components are soon to follow. In the case of code generation and O/R Mappers, sometimes the reusable code is used to generate more code.

As the role software plays in business becomes more important, the industrial-strength database platforms that used to live only within data centers have made their way out onto smaller, more personally manageable servers, and in some cases, on to desktop computers. Today the majority of all applications built use relational databases as their data storage mechanism. Thus, with the evolution of application development came the evolution of database drivers and the flurry of acronyms we see today, like ODBC, OLEDB, JDBC, DAO, RDO, and ADO. Although each of these database interaction libraries provides everything needed for applications to communicate with the database, they do little or nothing to help translate and persist the objects used by applications into SQL statements and data that can be stored by the relational databases. This work had to be done manually--meaning code had to be written by the programmer's hands every time.

For many years, developers repeatedly wrote the same data access layer code--methods called PersistChanges() or UpdateOrder(), which took actions such as building a SQL command to be sent to the database for processing, or updating a column value and having the database connectivity library handle the details of relaying that information to the database. There was very little variance among the actions taken by these types of methods that prompted programmers to consider building a general-purpose solution, something that could--with a little bit of information about the objects and data structure involved--automatically handle the tedium involved with CRUD (Create, Read, Update, Delete) operations. In the case of code generation, the idea is the same but, rather than a general purpose component, all of the code typically be written by hand is automatically generated based on database objects. It's just different sides of the same coin, you might say.

O/R Mappers and code generation started off with simple ideas and performed simple CRUD tasks easily. However, as these technologies have gained broader use, complexity has crept in. Most O/R Mappers on the market today have a special syntax to support specifying object criteria, such as a date range or ID value. Additionally, many O/R Mappers deal with a host of other concerns such as caching, concurrency, and validation, all of which are issues found in data access layer code.

Most database applications that use more than a handful of tables can benefit from O/R Mapping and code generation. The best way to determine if an O/R Mapper or code generation tool will help reduce your development costs is by taking a product for a spin and kicking the tires a bit. Although this guide will definitely help point you in the right direction, you should make an effort to evaluate products that interest you before settling on one in particular, which brings us to the topic of "how do I choose an O/R Mapper?"

What To Look For

Which O/R Mapper is best for you depends on your needs and preferences. Although there is a common level of functionality among almost every O/R Mapper, some provide more advanced features or can do code generation that the others do not. Some come with tools to help manage external configuration/mapping files, which may be important to you if you don't like editing files by hand. If price is an issue, you might take a closer look at the free components covered in this Guide. You may consider vendor support an important aspect of your purchase. Microsoft, the vendor of .NET itself, currently has an O/R Mapping framework named "ObjectSpaces" in development that, despite its delays, is aiming to provide developers with an O/R Mapping framework that will likely ship with a set of components packaged with Windows Vista upon its release. A little further in this Guide you will find a list of decision points that aim to provide you with a list of things to consider when evaluating an O/R Mapper for .NET.

Scenarios

There are a couple of different ways that you might want to incorporate an O/R Mapper or code generator into your software.

Although it's impossible to explore every possibility, this section of the Guide offers some general guidance to common scenarios.

Data Access Layer Components could be said to be the main target for O/R Mappers. Multi-DBMS support is important here, as your application might need to support more than one database as the storage mechanism. Support for transactions, null values, caching, stored procedures, SQL Logging, data-binding, and an OO-Query syntax are all considerations when using an O/R Mapper for a data access layer component.

CRUD (Create, Read, Update, Delete) code can be time consuming to write by hand. This process is also prone to errors, the likeliness of which increases with the more entities you have in your database. Using scripts or templates, code generators can help you automatically generate all of the code required to perform CRUD operations against your database in an object-oriented fashion. By repeating this process after any changes are made to your database schema, you can use a code generator to greatly reduce the amount of time required to maintain the synchronization between your object model and your data model.

Decision Points

With the number of O/R Mapping components on the market already, just the work it takes to find all the available choices can take an entire day. That's before you take the time to actually evaluate each product. Below is a list of decision points that you might want to keep in mind as you look at what each product has to offer.

Naturally, not all of these factors apply to every application.

The first thing to keep in mind is that no matter how much information we pack into this Guide, there's no substitute for trying the software in your own environment and on your own application. No one knows your own requirements, or the quirks of your own tools and components, better than you do. Fortunately, just about every vendor in the .NET tools and components business provides a trial version of their software for free evaluation. We recommend that you use this Guide to locate the O/R Mapping components that seem like a good fit for your application, and then download copies to evaluate them in your own environment. With O/R Mapping components, you'll find that evaluation copies normally display a nag dialog when certain features are accessed or are limited editions that do not contain some of the more advanced features that come when you purchase a licensed copy. This is not enough to interfere with evaluation, but generally precludes you from using an evaluation copy in a commercial application. Of course, you should follow the licensing requirements scrupulously in any case.

Trying before buying with O/R Mapping components is most important so that you can get a feel for the feature set of the component, how easy the API is to work with, and how well supported the component is with help files, documentation, source code examples, and design-time support. Some O/R Mapper vendors are happy to provide clients with free e-mail support during their evaluation period, while others may refer you to a knowledge base or forum for peer support. Some vendors also have How-To listings on their Web sites so that you can review code samples showing how to use their product in your application.

As of mid-2005, you might be working with .NET 1.0, .NET 1.1, a beta version of .NET 2.0, the .NET Compact Framework, or the Mono implementation of the .NET Common Language Runtime (a cross-platform open source implementation available for Windows and Linux). Although some O/R Mapper components are compatible in any of these environments, others have limitations such as using libraries not included with the .NET Compact Framework or not yet being compatible with new features in .NET 2.0. You'll need to verify that your vendor can match all of your target environments, or that they have a plan for doing so before your planned ship date.

Obviously, open source vendors allow you to access the source code behind their products. Surprisingly, so do some of the vendors that do not give away their product for free. Although some vendors charge extra or require special agreements to send you the source code, some will freely provide it with the product. This may be important to you if you require the ability to fix bugs or add features without relying on the vendor or if you'd like to be able to point the vendor to the problematic source code when you report it in order to get your support request resolved more quickly.

Some of the O/R Mapper components we reviewed made use of external XML mapping files that can become very lengthy depending on the number of entities you have in your system. Managing these files is simplified greatly if the vendor provides a utility for configuring them.

For applications accessing data that does not change frequently or only needs read-only access, caching can play an important role. Different methods of caching can be employed among O/R Mappers like a disk-based cache or in-memory. Additionally, some O/R Mappers can cache the object-relational mapping information in order to remove the need for accessing the mapping file repeatedly. As one of the most important requirements for implementing an O/R Mapping component is that there be no loss of performance, caching can make a big difference in whether your performance requirements are met or not.

The goal of some O/R Mappers is to remove all traces of SQL from your data access code. In place of SQL, some products support a proprietary syntax for specifying what is effectively your WHERE clause criteria. Other languages, like OPath as well as expression builders, and even raw SQL, are supported in some products. What works best for you and which method of query expression you're most comfortable with might help narrow down your choices of O/R Mappers to consider. Other considerations to make in this area are whether or not you anticipate needing support for DBMS-proprietary keywords in your SQL statements, such as the TO_DATE() function in Oracle.

Some O/R Mappers are said to be "non-intrusive" or to support POCO (Plain old CLR Objects) because they allow you to take your existing object model (or the objects generated by a code generator) and, with a little configuration work, map them to the existing database structure. If you have an existing object library and are looking to port it over to using an O/R Mapper or code generator, this might be a feature you'll want to look out for.

Features

General Features

These are features that apply broadly across many types of software.

• Managed Code - The product is 100% managed code, as opposed to unmanaged code or a managed code wrapper around unmanaged code.
• Integrated Help - The product provides a help file integrated directly with the Visual Studio .NET help file.
• External Help - The product provides an external help file.
• Documentation - The product provides documentation beyond a help file, such as a manual or code samples.
• Peer Support - There are peer support options, such as newsgroups or discussion boards, available for the product.
• Vendor support - The vendor provides direct support options for the product, either as part of the purchase price or as a separate support contract.
• .NET Framework 1.0 Support - The product includes a version that works with the .NET Framework 1.0.
• .NET Framework 1.1 Support - The product includes a version that works with the .NET Framework 1.1.
• .NET Framework 2.0 Support - The product includes a version that works with the .NET Framework 2.0.
• Compact Framework Support - The product includes a version that works with the .NET Compact Framework.

Object-Relational Features

• OO-Query Support - The product supports a parameterized or free-form text format for specifying object criteria.
• External Mappings - The product supports using an XML or other file format to store the object-database mappings.
• Internal/Attribute Mapping - The product supports using code attributes or internal mapping instructions.
• Multiple DBMS Support - The product supports more than one Database Management System.
• Databinding Support - The product supports data binding to object fields.
• Stored Procedures - The product supports calling Stored Procedures for CRUD operations.
• Mapping Configuration Tool - The product provides a tool to manage the mapping configuration file(s).
• Generics Support - The product supports generic types in .NET 2.0.
• SQL Logging/Spooling - The product supports spooling any SQL statements executed against the database to a log file.
• Lazy Loading - The product supports lazy loading of data into an object model/hierarchy.
• Code Generation - The product supports generating the code--classes and data access--necessary for translating your objects into database records and vice versa.
• Server-side Paging - The product supports getting only the data it needs from the server, rather than retrieving the entire data set from the server and then filtering the view of the data on the client computer.
• Caching - The product supports the caching of data locally using the disk or in-memory.

Vendors/Software Authors in this Guide

Products Profiled in this Guide

AgileStudio

Version 2.2, Starts at $229
Download it here
Licensing: Proprietary

AgileStudio provides a Visual Studio .NET add-in that allows you to set up connections to your database, define the objects you want to work with, and then creates typed datasets and Windows Forms controls based on your choices. AgileStudio requires using the .NET InstallUtil utility to install the AgilePages DataStore Manager Windows Service, which handles the interaction between the Visual Studio .NET add-in and your database, either SQL Server or XML files. Then, using the Visual Studio .NET add-in, you can define new objects and their members, and map these to your data store. Once your data store is configured, AgileStudio adds some .NET components (AgilePagesDataSetManager and AgilePagesConnection) to your form to help manage the interaction with the database, and automatically generates the code required to persist changes made with the application. Support for AgileStudio is provided through an online Knowledge Base at the vendor's Web site or through e-mail.

Atoms Framework

Version 2.2, Free
Download it here
Licensing: LGPL

The ATOMS Framework Project is an open source O/R Mapper project for Visual Studio .NET that provides object persistence using several database providers including Firebird, Informix, MaxDB, Microsoft SQL Server, MySQL, Oracle, and PostgreSQL. To use the ATOMS Framework, you can register the component provided by the vendor in the GAC on the your development computer or add a reference to it in your project. Also available from the vendor are some sample projects and NUnit tests to show you how to use the ATOMS Framework. Support for the ATOMS Framework is provided through the public forums at the SourceForge project page.

BBA Data Objects

Version 1.2.0, Free
Download it here
Licensing: LGPL

BBA DataObjects is an object-to-relational mapping library for .NET that maps SQL Server tables to objects. Top features include lazy loading, paged loading, and cryptography. BBA DataObject works by having you create classes that inherit from classes in the BBA DataObjects library, which handle persisting the object to the database automatically. Support for BBA DataObjects is provided through public forums at the SourceForge project home page (which looks fairly quiet) and through e-mailing the SourceForge project owner.

BizBlox

Version 0.9.9.1, Free?
Download it here
Licensing: Proprietary

BizBlox is a code generation tool that generates its code from SQL scripts exported from SQL Server Enterprise Manager, Query Analyzer, or scripts you may have written by hand. This generated code implements the BizBlox ORM API to automatically persist the objects to the database. BizBlox supports code synchornization for the code it generates, so that changes to the data schema (scripts) can be made and then reflected in the generated code upon the generation of the code. One of the requirements of BizBlox is that you use the uniqueidentifier data in your primary keys since BizBlox implements the GUID data type for the primary key value in its tables. From within the Visual Studio .NET IDE, you can use the BizBlox ORM API with your own objects by adding a reference to the BizBlox ORM components to your project. The BizBlox architecture makes use of the transfer object design pattern, which places importance on fast distributed-object communication for data access objects. Support for BizBlox is provided through an online Knowledge Base at the vendor's Web site.

Codus

Version 1.1.0.0, Free
Download it here
Licensing: Apache License 2.0

Codus is a code-generation tool for object-relational mapping that provides a wizard-like tool to guide you through the process of defining a database connection, choosing the tables or views you'd like to generate code to interact with, choosing a code generation template, and then generating the code itself. Additionally, Codus gives you the ability to generate NUnit tests, NAnt build files, VS.NET solution files, Web Services, stored procedures, and Zanebug tests (Zanebug is a unit testing product by Adapdev). Currently, Codus supports Microsoft SQL Server, Microsoft Access, and Oracle with plans to support MySql in the near future. Support for Codus is provided via online forums or by e-mail.

DADO Object Mapper

Version 1.1, Starts at $99
Download it here
Licensing: Proprietary

DADO Object Mapper is an O/R Mapper that also can work in conjunction with DADO's Application Server and Broker System all bunded together to provide a framework for multi-tier distributed object-oriented enterprise applications. DADO Mapping Studio is the front-end O/R Mapper that provides a tool for managing your O/R mapping projects, as shown in the screenshot. Using this tool you can import objects from several different database systems including SQL Server, Oracle, MySQL, DB2, and Microsoft Access. Mapping is handled using an XML file that you can manage from the Mapping Studio application. Support for DADO Object Mapper is handled via e-mail or by more direct means if you purchase DADO's greater support package. Source code for the framework can also be requested by e-mailing the vendor.

DataBlock

Version 1.1, 150 euros
Download it here
Licensing: Proprietary

DataBlock is a code generation tool that allows you to generate database platform neutral code in either C# or Visual Basic .NET from the data model and schema information found within your database. DataBlock supports Microsoft SQL Server, Microsoft Access, and MySql. All mapping and configuration settings are output via code attributes and are compiled into the .NET assembly. These mappings are also controllable through the GUI code generation tool. Customer Support for DataBlock is handled via e-mail and phone. Customers may also receive the source code to DataBlock, which enables you to make changes to the way the mapping and code generation is performed by the tool.

Data Mapper

Version 1.1.1845.40237, Starts free, $70 for Standard Edition, $120 for Professional Edition.
Download it here
Licensing: Community, Standard, Professional

Latticesoft Data Mapper is a .NET object-based persistence library for relational databases that supports SQL Server, Oracle, and OLEDB-accessible databases using external XML configuration and mapping files. Objects can also be mapped to stored procedures or static SQL statements. To use the Data Mapper, you install the Data Mapper persistence framework on your computer and reference the Data Mapper assembly in your projects. Data Mapper also comes with a utility called SPGen that can auto-generate CRUD stored procedures for each table and view in SQL Server, Oracle, and DB2 databases. Support for Data Mapper is provided via an online request form.

DataObjects.NET

Version 3.5, starts at $299, volume discounts available
Download it here
Licensing: Proprietary

DataObjects.NET is an object persistence framework that, in addition to providing O/R Mapping features, also provides business object services similar to .NET Enterprise Services, such as transaction management, security (ACLs), and automatic handling of Remoting. DataObjects.NET supports several database systems such as SQL Server (including version 2005), Oracle, Microsoft Access, MSDE 2000, Firebird, and MaxDB. DataObjects.NET also supports all object-oriented features like inheritance (including interfaces), and allows you to query against the whole inheritance hierarchy of a persistent type or interface. Support for DataObjects.NET is provided via online forums or by e-mail.

EdgeXtend for C#

Version 9.004,
Download it here
Licensing: Proprietary

EdgeXTend is a code generation tool that generates C# data access layer code for .NET applications. A code generation tool is provided that allows you to define your classes and their members for your object model. At run-time, the generated code makes use of Persistence's O/R Mapping, caching, and synchronization (if desired). Caching instructions can be stored in a separate XML file, and can be made to work in a clustered environment if the need to scale your application arises. Support for EdgeXTend includes many options such as an online Knowledge Base, e-mail support, online documentation, support programs and services, and Live!Debug sessions where you can allow a support agent to take control of your computer to help.

Evolve .NET Data Access Objects

Version 1.3.1, Free
Download it here
Licensing: LGPL

Evolve .NET Data Access Objects consists of three components. First, a data access layer for accessing a relational database over an abstract layer. Second are Persistence Containers, which are an O/R Mapping layer used to handle CRUD operations. Lastly, .NET Data Access Objects provides a Visual Studio .NET add-in to assist in helping you define the mapping information used by the Persistence Containers. This mapping information is stored in XML files. Support for Evolve .NET Data Access Objects is provided via public forums at the SourceForge project home page and by e-mailing the SourceForge project owner.

eXpress Persistent Objects for .NET

Version 1.5, $199 with source code, $149 without.
Download it here
Licensing: Proprietary

eXpress Persistent Objects for .NET, or XPO is an O/R Mapping framework designed to fully shield the developer from the database. To use XPO, you develop objects that inherit from XPO's persistent objects, and XPO generates the database for them automatically. XPO also automatically handles the relationships between classes and object inheritance. Not everything is out of your hands, however. If you require more precise control over the way the O/R Mapping is performed, you can make use of XPO's built-in code attributes to provide more explicit mapping instructions to XPO. You can specify retrieval, sorting, and filtering criteria using straightforward object syntax provided by the framework. XPO presently supports Microsoft Access, Microsoft SQL Server, MySQL, Oracle, PostgreSql, Firebird, and Advantage database systems. XPO comes with full source code available if you decide to purchase it. Support for XPO is provided via an online knowledge base, forums, and newsgroups.

Genome

Version 2.2.10, Starts at € 299
Download it here
Licensing: Proprietary

Genome is an O/R Mapping tool that provides automated persistence for .NET classes. OQL is supported as the language with which to specify object criteria. Another useful feature of Genome is its ability to generate DDL scripts for any given business layer-to-database mapping. Genome's mapping information is stored in XML files that can be edited by hand. Genome also supports features like result paging, partial object loading, and greedy loading hints in order to help with performance. Support for Genome is available via newsgroups at news://news.techtalk.at/techtalk.public.genome.support and also through incident report requests and by e-mail. Genome also offers extra services like architectural support/reviews, developer coaching, and code reviews.

Gentle.NET

Version 1.2.5, Free
Download it here
Licensing: LGPL

Gentle.NET is a free, database independent object persistence framework. It features automatic SQL generation and object construction, a SQL factory for creating custom queries, DataView construction helpers, and more. Gentle.NET supports providers for Oracle, PostgreSQL, MySql, Firebird, SQL Server, MSDE, Access, SQLite, and Sybase. Using Gentle.NET requires adding references to a few different Gentle.NET assemblies and then providing configuration settings for database connection strings, database providers, etc. From there, Gentle.NET automatically handles persisting the objects that you have placed certain attributes on, such as the TableName attribute for classes, and the TableColumn attribute for members. Support for Gentle.NET is provided at the SourceForge project public forums and at the Gentle.NET Community page found at http://www.mertner.com/confluence/display/Community/Home.

Grove

Version 1.0.1654.34510, Free
Download it here
Licensing: Open Source

Grove is an O/R Mapping component library for .NET requiring that each object needing persistence contain an attribute that lists the table name from the data source such as [DataTable("Orders")]. These attributes also let you specify information such as join types for multi-table objects and primary and foreign key information for class members. Grove supports basic transactions through methods like BeginTransaction, Commit, and Rollback, and supports SQL Server, OLEDB, and ODBC Data Sources. Methods taken to get support for Grove are not clear from the vendor's Web site, although e-mail addresses for the Grove team are provided.

iBatis Data Mapper

Version 1.2.1, Free
Download it here
Licensing: Apache License 2.0

iBATIS DataMapper is a Java/.NET framework meant to help design and implement persistence layers for Java/.NET applications. iBATIS couples objects with stored procedures or SQL statements using an XML mapping file. iBATIS Data Mapper supports providers for Access, SQL Server, Oracle, MySql, PostgreSQL, DB2, and generic ODBC and OLEDB providers. Using the XML mapping file, the iBATIS framework allows you to query for the objects you want, and returns them to you using the IList interface. Support for iBatis Data Mapper is provided by FAQ, a Wiki, mailing lists, and a bug submission tool, all found on the vendor's Web site.

Itec Data Layer

Version 2.0, Starts at $17
Download it here
Licensing: Proprietary

Itec Data Layer comes in the form of an application called MyCodeGenerator that is a code editor and a code generator. You can create your own projects and templates within MyCodeGenerator to tweak the structure used in generating the code. Additionally, the code generated can make use of the Data Access Application Block and the Exception Management Block that are part of Microsoft's Enterprise Library. MyCodeGenerator supports code generation for either C# or Visual Basic .NET and allows you to specify a default namespace name for the generated code. MyCodeGenerator also has the ability to create and use Stored procedures for your project and can generate typed datasets using the XSD.exe utility. Support for MyCodeGenerator is via e-mail.

LLBLGen Pro

Version 1.0.2004.2, € 229
Download it here
Licensing: Proprietary

LLBLGenPro is both an O/R Mapper and a code generation tool for .NET that generates a complete data-access tier and business object tier for either C# or Visual Basic .NET based on an existing database schema. LLBLGenPro makes use of the provider model for database access architecture and supports SQL Server, Oracle, Access, MySQL, Firebird, the IBM DB2 UDB.NET provider. LLBLGenPro's Code Generation and O/R Mapper work in conjunction with each other in that once you have generated your project's code, you then reference the LLBLGenPro ORM support library in the client project and have ORM support for the code generated by the tool. Support for LLBLGenPro is provided via forums on the vendor's Web site and via e-mail (directly or through a Web contact form). Also, many sample projects are available for download on the vendor's Web site.

My Generation

Version 1.1.3, Free
Download it here
Licensing: Free

MyGeneration is a free code-generation tool that executes templates to convert database schema objects into object models, stored procedures, markup languages, and ASP.NET pages. These templates can be written in a variety of languages including Visual Basic .NET, C#, VBScript, and JScript. Each language has the ability to mix literal content and executable or interpreted code using the syntax introduced by classic ASP (<% %> tags). One of the unique features of MyGeneration is that it works just as well for COM code as it does for .NET. The two scripting languages provide a pathway to scripting against COM objects via the CreateObject() method and the two .NET languages allow coding with the .NET Framework. MyGeneration supports Microsoft SQL Server, Microsoft Access, Oracle, IBM DB2, MySQL, Postgre SQL, FireBird, Interbase, SQLite, and VistaDB. Support for MyGeneration is provided via online forums at the vendor's Web site.

NDO

Version 1.1, Free to 1.999,-€
Download it here
Licensing: Proprietary

NDO (.NET Data Objects) is an O/R Mapping development tool that allows you to dress your objects with certain attributes and have them persisted to a database such as SQL Server, Oracle, MySql, Access, or Firebird--the databases which NDO supports. NDO also provides a mapping tool called The Enhancer to help you manage the XML file used to store the information about your mapping configuration (as shown in the screenshot). The Enhancer is also capable of generating SQL DDL scripts you can use to create database objects. For classes you want persisted by NDO, you add an attribute of [NDOPersistent] to your class. Support for NDO is provided by e-mail only.

Neo

Version 1.3.2, Free
Download it here
Licensing: LGPL

The NEO (.NET Entity Objects) Framework is an O/R Mapping component and custom code-generation library that dynamically generates the SQL necessary to perform CRUD operations for your objects at run-time based on mapping information stored in an XML file. NEO is based on the ADO.NET DataSet object and can persist objects to an XML file as well as a relational database system. As you update your schema (mapping) file, NEO automatically creates the base classes and creates individual files for each entity class. Support for NEO is provided by a Wiki hosted at the vendor's Web site, and there is also public access to an issue-tracking system for the product. Mailing lists are also available for both users and developers.

NHibernate

Version 0.9, Free
Download it here
Licensing: LGPL

NHibernate is a .NET based port of the Java Hibernate object persistence library for relational databases. NHibernate handles persisting your .NET objects to and from a relational database using an XML configuration file for the mapping information, including the names of your types, the providers for the database to be used, and the database connection information. Once you've created the tables to persist your objects to, and created your objects to persist, you can set up your configuration file and start using the NHibernate API to get and persist all of the objects in assemblies NHibernate is aware of. NHibernate supports Access, DB2, Firebird, MySql, PostgeSQL, SQL Server 2000, and SQLite. Support for NHibernate is provided through public forums at the SourceForge project home and a public developer mailing list.

Nolics.NET

Version 2.1 and 2005, $585
Download it here
Licensing: Proprietary

The Nolics.NET productivity tool consists of an O/R Mapper and several domain-specific languages. Nolics.net supports standard data bindings for Windows Forms applications. For ASP.NET applications, in addition to the standard data bindings, Nolics.net supports two-way data bindings with automatic support for control enabling/disabling (the controls are automatically enabled if the object bound to the controls becomes modifiable). Nolics.NET also supports inheritance, identity, parent-to-child relations, and importing existing legacy databases. Support is provided for Nolics.NET through online FAQs, e-mail, online demos, and online documentation.

NPersist

Version 1.0.8, Free
Download it here
Licensing: LGPL

The NPersist Framework is a free open source .NET O/R Mapping persistence framework for version 1.1 (or later) of the .NET Framework. Although it is written in C#, it supports persisting objects written in any .NET language. Mapping information for NPersist is stored in an XML file that can be generated by using the MatsSoft ObjectMapper 2005 application available at http://www.objectmapper.com/Home/Default.aspx. Support for NPersist is provided through public message boards at the GotDotNet Workspace project home for NPersist at http://workspaces.gotdotnet.com/npersist and forums and bug listings at the NPersist home page. Online documentation is also available as well as an NPersist newsgroup at news://magpie.sytes.net.

ObjectBroker

Version 0.1.0, Free
Download it here
Licensing: BSD License

ObjectBroker is an O/R Mapping framework for the .NET platform. Its main features consist of transparent persistance and transaction management. Mapping configuration settings are stored in an XML file. The transaction management features of ObjectBroker are based on COM+ Enterprise Services. Support for ObjectBroker is provided by the public forums at the products SourceForge home page and via e-mail.

Objectz.NET

Version 2.2, Starts at $49.95
Download it here
Licensing: Proprietary

Objectz.NET is an O/R Mapping Library for .NET that lets you map the properties and fields of your .NET application classes directly to your database tables, columns and views. The Objectz.NET Mapping Studio application is the user interface that provides an easy way to graphically map classes to the database. The Objectz.NET Mapping Studio also allows you to define one or several database connections to use and which .NET assemblies to include in your project. You can then pick individual classes to map to database objects. Classes can be mapped to both tables or views from your data source, and individual class members are mapped to columns in the chosen tables. Source code is available for an additional cost. Support for Objectz.NET is provided via online forums at the vendor's Web site.

OJB.NET

Version 0.8.2419.0556, Free
Download it here
Licensing: LGPL

OJB.NET enables you to persist data between your .NET business objects and your relational database. OJB.NET also enables you to reverse-engineer your database (similar to Visio's database diagrams), to automatically generate .NET classes, and to get and persist your objects at runtime. OJB.NET allows lazy loading of objects and also automatically creates the mapping configuration between your objects and database tables. Support for OJB.NET is provided by the public forum at the SourceForge project forum.

OPF.NET

Version 1.0.0.864, Free for non-commercial development
Download it here
Licensing: GPL

The Object Persistence Framework for .NET (OPF.NET) is an O/R Mapping class library that can manage object retrieval from and persistence to relational database systems and other persistent storage mechanisms, such as XML files. OPF.NET works by having your objects inherit from various classes like the Persistent, Collection, CollectionSqlDataManager, and PersistentSqlDataManager classes in order to perform standard CRUD-type operations in your objects. OPF.NET fully supports transactions for all database systems that support transactions. Currently OPF.NET offers storage classes for Microsoft SQL Server, ADO, OLEDB, and ODBC. OPF.NET has also made recent performance enhancements to speed up data access by implementing the ADO.NET DataReader internally. OPF.NET also offers an OPF.NET Studio product which is a business object generator based on OPF.NET. It allows you to automatically create business objects and create test cases for NUnit. Support for OPF.NET is provided via online forums, code snippets, and online documentation.

Opf3

Version 3.0.2, Starts at $199.95, volume discounts available
Download it here
Licensing: Proprietary

Opf3 is an object persistence framework for .NET 2.0 that provides a large set of sample/tutorial projects for you to see how the framework works. Opf3 uses code attributes and reflection to handle the mapping of Object fields to database table columns. The vendor's Web site has a PowerPoint tutorial that shows how to make use of the framework for creating and persisting objects using the Opf3 framework. The samples we downloaded require Visual Studio 2005 and can not be opened by Visual Studio 2003. Database support is strong as the Opf3 framework supports Microsoft SQL Server, Oracle, VistaDB, Postgre SQL, Microsoft Access, and Pervasive SQL. OPath is the object query language used by the Opf3 framework and supports raw SQL for sorting and grouping purposes. Support for Opf3 is provided via e-mail and annual priority e-mail support is available for purchase from the vendor's Web site.

ORM Framework

Version 1.1, Starts at $119
Download it here
Licensing: Per server, per site

The ARBT ORM Framework consists of abstract objects you can inherit from in your code. Your objects can inherit the functionality needed to automatically retrieve and persist data from Microsoft SQL Server, Oracle, and any other data source accessible via ADO.NET. The ORM Framework also allows you to store and retrieve data via XML, and bypass a database completely. Mapping configurations for the product can be managed using either database views or XML files containing the description of database objects and classes in your code. The code provided for the abstract objects is 100% managed code written in C#. Support for the ORM Framework is handled via e-mail.

ORM.NET

Version 1.7.2.32067, Free
Download it here
Licensing: LGPL

ORM.NET is a code generation tool capable of outputting either Visual Basic .NET or C# code. ORM.NET uses a fairly simple wizard application (shown in the screen shot) to take you through connecting to the database, choosing for which tables you'd like to generate code, and then customizing some settings (such as the name of your namespace and the type of method signatures on your public accessor methods) and then you can set off the process of ORM.NET generating a set of classes that you can compile into a library to use to persist all of your objects. ORM.NET comes with a complete documentation file that includes API information, a quick start guide, and information on sample applications. Support for ORM.NET is provided via e-mail, phone, or at the public forums on the SourceForce project site.

Pragmatier.Persistence

Version 2.6.5.1, Free
Download it here
Licensing: GNU LESSER GENERAL PUBLIC LICENSE

Pragmatier.Persistence is a GotDotNet Workspaces project that is the result of the company Pragmatier going out of business. Pragmatier open-sourced their core component, so the Visual Basic .NET source code is freely available to all. It has been updated to support v1.1 of the .NET Framework and supports ODBC data sources. Unfortunately, no documentation or support accompanies the source code, so getting up to speed with the code might take longer than with other open source offerings.

Retina.NET

Version 1.0.0.6, Free
Download it here
Licensing: Shared Source

Retina.NET is a GotDotNet workspaces project for an open source O/R Mapping library. Using Retina.NET is very straightforward. Objects that want to make use of Retina.NET inherit from the Retina.Core.Entity class. Make sure your object provides a parameterless constructor and mark the primary key member of the class with an attribute. After that, you're all set. Retina.NET ensures that the database schema objects (including constraints) maintain the rules you have laid out for your objects. Retina.NET also has support for lazy loading of child objects through the use of proxy objects. Retina.NET comes with a Quick Start document (an MS word file) that lists many examples of how to use Retina.NET, code samples included. Support for Retina.NET can be found on the Retina.NET Workspace message board.

Sooda

Version 0.7, Free
Download it here
Licensing: BSD License

Sooda is an acronym for Simple Object-Oriented Data Access and is a code generation tool that supports any .NET language that has a CodeDOM provider. With Sooda, you can auto-generate all of the code needed for an object-oriented data access layer and reduce the amount of CRUD code to a minimum. In addition to v1.1 of the .NET Framework, Sooda also supports Mono. Nant 0.85 is supported as an alternative to using Visual Studio 2003 for compiling the code produced by Sooda. It is not clear on the vendor's Web site how to get support for Sooda. but it appears that e-mail to the vendor gets you a prompt reply.

Versant Open Access for the Microsoft .NET Framework

Version 3.4.4.86, $995
Download it here
Licensing: Per developer

Versant Open Access for the .NET Framework is an O/R Mapping persistence framework that offers object persistence through changes made to the IL produced by the compiler and thus works with any IL-compatible language. Object querying can be done either using OQL or SQL directly and supports SQL Server, Oracle, and DB2 databases. Versant Open Access also provides a mapping designer that can be used to map your database tables to objects or, going in the other direction, to create objects based on an existing database schema. Support for Versant Open Access is provided via community forums, or you can initiate an ad hoc support request by visiting the Versant eShop. E-mail and phone-based support is also available for critical issues.

Wilson ORMapper for .NET

Version 4.0, $50
Download it here
Licensing: Proprietary

Wilson ORMapper for .NET is an O/R Mapping library that transparently persists your business objects according to the rules defined in an XML mapping file. To use Wilson ORMapper from Visual Studio .NET, you add a project reference to the WilsonORMapper.dll file. After you have written the code for your classes and created your mapping file for those classes, you create an instance of the ObjectSpace class from the Wilson.ORMapper namespace, and pass the path of the mapping file, a connection string, and the type of database provider you want to use to the ObjectSpace constructor. From there, persisting your object is as easy as calling methods like PersistChanges() to save an object or GetObjectSet() to retrieve a series of objects. Wilson OR Mapper for .NET supports Microsoft SQL Server, Oracle, Microsoft Access, and ANSI compliant database systems. Support for Wilson ORMapper is provided via forums on the vendor's Web site and you can also e-mail the vendor with questions.

General Criteria

What things should you consider when purchasing any type of third party development tool or component? Or when deciding between purchasing such a component and building it in-house? Here are some factors you might like to think about:

Note: Be careful with very large vendors that are not focused in the area of your interest. Large vendors have a bad habit of becoming interested in developer tools yet quickly drop support when they realize how hard it is to make money selling components and tools to developers. Exceptions are when the developer tools are their core competency or support their strategic direction. Conversely, don't discount small vendors if they have been in business for a while and have shown a proven ability to focus and provide quality products.

Feature Tables

Products Not Profiled in this Guide

These are the products appropriate for this Guide but for one reason or another we did not cover. In some cases, we simply didn't locate the products in time to include them in this edition of the Guide, and hope to add them to the next revision. In others, they declined to participate and refused to send us a license for evaluation. We list these products and their URLs here so you can research them on your own if you like.

Alachisoft Tier Developer
http://www.alachisoft.com/tdev/overview.html

Evaluant Data Tier Modeler
http://www.evaluant.com/en/solutions/dtm/default.aspx

MatsSoft ObjectMapper 2005
http://www.objectmapper.com/Home/Default.aspx

Olero Software ORM.NET
http://www.olero.com/OrmWeb/

POTIS Object-Relational Toolkit
http://www.port.com.pl/

prettyObjects ABC.NET
http://en.www.prettyobjects.com/abc.net.aspx?sid=overview

Revelation Technologies Dali
http://www.revtechnologies.com/Dali.aspx

SharpPower RapTier
http://www.sharppower.com/Default.aspx?path=products/RapTier

Thoma Consulting EntityBroker
http://www.thona-consulting.com/content/products/entitybroker.aspx

Carlos Silva-Santisteban Silvtek.ORM
http://www.silvtek.com/ORM/howto/index.html

Informed Opinions

We asked a variety of well-known leading-edge developers with significant credentials their opinion regarding the most important criteria for selecting an object-relational mapping tool for .NET. Their "Informed Opinions" follow: