WilsonORMapper is the open source release of Paul Wilson's O/R Mapper. It is lightweight, powerful, and easy-to-use.

Originally hosted at http://www.ormapper.net, the open source release was made official on Sept 9 2007 by Paul Wilson (read his announcement), as of version 4.2.2.0.

.NET v2.0 Support

• Supports both Generics and Nullable Types with the .NET v2.0 Build.

Database Support

• Supports MS Sql, Access, Oracle, as well as generic OleDb and Odbc.
• Define your own CustomProvider for any Database without Recompile:
• MySql, PostgreSql, Sqlite, Firebird, DB2, VistaDB, Sybase, etc.
• Retrieve individual objects by key -- auto, guids, and user-entered.
• Use auto key-types with Oracle 9+ by setting trigger with sequence.
• Composite keys supported, even with relations and stored procs.
• Supports one-to-many, many-to-one, and many-to-many relationships.
• Supports outer joins to populate lookup values in a single query.
• Supports optional lazy-loading to minimize reads from the database.
• Supports optional default sort orders that are always overridable.
• Supports optional field default null-values -- thanks to Tim Byng.
• Even use null-value expressions like MinValue -- thanks to Jeff Lanning.
• Use any raw sql statement with GetDataSet or ExecuteCommand.

Retrieval Support

• Retrieve individual objects by primary key, often from internal cache.
• Retrieve collections as a static ObjectSet or a cursor ObjectReader.
• GetCollection returns strongly typed collections -- thanks to Allan Ritchie.
• Retrieve DataSets, optionally specifying a specific subset of fields.
• Query with any where and sort clauses -- use sql or the QueryHelper.
• Build simple expressions with an OPath-like syntax using the QueryHelper.
• Includes nearly complete OPath query engine -- thanks to Jeff Lanning.
• Supports paged collections -- queries can specify page index and size.
• Can optionally use stored procedures with parameter for any retrieval.
• Performance is very much comparable, sometimes better, than DataSets.
• Support for Typed Datasets which some Reporting Packages Require.

Persistence Support

• Explicitly create objects with new and StartTracking, or use GetObject.
• Persist individual objects, or a collection of objects in transaction.
• Control your own Transaction object with BeginTransaction method.
• Interact with the Transaction in the IObjectNotification events.
• Thanks to Ken Muse for recursive persistence and cascading delete help.
• Recursively persist all related child changes with PersistDepth.ObjectGraph.
• Optionally enable cascading deletes on any relation in the xml mappings.
• User can define fields for optimistic concurrency, or read-only fields.
• Updates can optionally be only the changes, with or without concurrency.
• Execute set based updates and deletes, including update set expressions.
• Persistence is done with safe and efficient parameterized dynamic sql,
• although stored procedures can optionally be configured for persistence.
• Supports optional before and after event notification for persistence.

Simple Architecture

• No need to inherit objects from a base class or embed any attributes.
• Map either member fields or properties, with reflection or interface.
• Object-relational mappings are made in one or more simple xml files.
• Optionally use embedded resources for mappings -- thanks to Allan Ritchie.
• Support class hierarchies and simple mapping inheritance by Jerry Shea.
• Also supports "shared inheritance" in the database using type discriminator.
• Optionally intercept database commands for logging or even modifications.
• Includes a Windows ORHelper to generate the mapping and class files.
• Also includes CodeSmith Templates from Paul Welter for code generation.
• Collections support one-way read-only binding for both Web and Windows.
• Separate instances can be created for multiple databases or providers.
• Easy to deploy with simple x-copy in shared web hosting environments.
• Supports medium-trust when mapping to public members (or reflection).
• Includes full C# source code, as well as the rest of WilsonDotNet.com.