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❗ Important ❗

We discovered a serious issue connected to entity saving to storage for provider that use batching. Though its appearance is rare, version update is strongly recommended.

Minimal versions in which the issue is addressed: 6.0.12, 7.0.4, 7.1.1

The master branch also has the fix merged (commit f642a25).

If you forked the repository then make sure that this fix will propagate to your fork and branches.


DataObjects.Net is a persistence and object-relational mapping framework for the Microsoft .NET. It allows developers to define persistent objects as well as business logic directly in C#, Visual Basic or F#. The persistent objects can be retrieved by LINQ queries. Persistent data can be stored in SQL Servers. In contrast to many other ORM frameworks the database model is generated and maintained automatically.

Supported databases:

  • MS SQL Server 2008 R2, 2012, 2014, 2016, 2017, 2019, 2022
  • MS Azure SQL Database
  • Oracle 10g, 11g
  • PostgreSQL 8.3, 8.4, 9.0, 9.1, 9.2, 10, 11, 12, 13, 14, 15
  • MySQL 5.6, 5.7, 8.0
  • Firebird 2.5, 4.0
  • Sqlite 3

NOTE that MS SQL Server 2008 R2, PostgreSQL v8.3, v8.4, and MySQL v5.5 were removed from supported versions list because they're too old and reached End-Of-Live status. Drivers for these versions still exist within libraries and we will try to keep them working but no guarantee given.


DataObjects.Net is available on Nuget. Install main package (NOTE this package does not include any providers, install needed provider addtionally)

dotnet add package Xtensive.Orm

Providers for MS SQL Server, Oracle, PostgreSQL, Mysql, Firebird and SQLite may be installed following way

dotnet add package Xtensive.Orm.SqlServer
dotnet add package Xtensive.Orm.Oracle
dotnet add package Xtensive.Orm.PostgreSQL
dotnet add package Xtensive.Orm.MySql
dotnet add package Xtensive.Orm.Firebird
dotnet add package Xtensive.Orm.Sqlite

DataObjects.Net extensions are available on Nuget as well (more about extensions here)

dotnet add package Xtensive.Orm.BulkOperations
dotnet add package Xtensive.Orm.Localization
dotnet add package Xtensive.Orm.Logging.log4net
dotnet add package Xtensive.Orm.Reprocessing
dotnet add package Xtensive.Orm.Security
dotnet add package Xtensive.Orm.Tracking
dotnet add package Xtensive.Orm.Web

Use the --version option to specify version to install


The following code demonstrates basic usage of DataObjects.Net. For full tutorial configuring Domain, defining the model and querying data see our documentation.

// create configuration with connection to Tests database on local instance of MS SQL Server
var domainConfiguration = new DomainConfiguration(@"sqlserver://localhost/Tests");
// register types from certain domain
domainConfiguration.Types.Register(typeof (Person).Assembly, typeof (Person).Namespace);
// create database structure from scratch
domainConfiguration.UpgradeMode = DomainUpgradeMode.Recreate;

// on application start build Domain
var domain = Domain.Build(domainConfiguration);

// open a session to database
using (var session = domain.OpenSession()) {
  using (var transactionScope = session.OpenTransaction()) {
    // query for existing Anton Chekhov
    Author existingAuthor = session.Query.All<Author>()
      .Where(author => author.FirstName=="Anton" && author.LastName=="Chekhov")

    //if Anton Pavlovich isn't in database yet then and him
    if (existingAuthor==null) {
      existingAuthor = new new Author(session) {
        FirstName = "Anton",
        LastName = "Chekhov";

    // add new book and assign it with Anton Chekhov
    existingAuthor.Books.Add(new Book(session) {Title = "The Cherry Orchard"});

    // commit opened transaction to save changes made within it

// on application shutdown dispose existing domain

Getting support

If you have a specific question about using DataObjects.Net you can ask on our support forum or send your question to

How To Build

Repository contains one solution file - Orm

This solution contains Weaver project responsible for post-build processing of assemblies containing inheritors of Xtensive.Orm.Persistent class. Weaver project is first in build sequence. Other projects in the solution include DataObjects.Net itself as well as its extensions and tests.

In order to build project binaries one need to execute the dotnet build command in the solution folder. It will build everything in Debug configuration. In case Release binaries are needed just specify configuration parameter as following

dotnet build -c Release

By defuault Debug configuration build doesn't generate Nuget packages but Release configuration build does. It is possible to change this default behavior by specifying GeneratePackageOnBuild parameter explicitly. So in case Nuget packages aren't needed for release build consider to run

dotnet build -c Release /p:GeneratePackageOnBuild=false

alternatively the following command will generate packages for Debug build

dotnet build /p:GeneratePackageOnBuild=true

Build results are available in the _Build subdirectory of solution folder.

Version.props file declares version is building. <DoVersion> tag defiles version in <Major version>.<Minor version>.<Revision> format. Do not define Build number, it is defined while building. <DoVersionSuffix> should be defined for pre-release versions like Alphas, Betas, and RCs.


DataObjects.Net and its extensions published here are licensed under the MIT license.