Can I connect an XAF application to a custom data source (Web service, OData service, NoSQL database, etc.)?

My colleague Michael and I have recently worked on the article clarifying the currently supported data stores for XAF, because from time to time we receive questions like the one above. Even though this is a very basic information, it is still worth checking out even if you already have some XAF experience. Please let me know if there are any questions on this.

XAF is a framework designed to visualize and work with data represented as business or domain objects. The object-relational mapping (ORM) concept is very important here as in our framework you should not normally think of database tables, stored procedures (SP), SQL statements, but rather operate data in an object-oriented manner. Check out the Business Classes vs Database Tables article and information about Domain Driven Design (DDD) to get more inspirations. To access and manipulate objects, queries for all CRUD operations are performed dynamically based on view properties via the IObjectSpace API in a unified way. This design implies certain requirements to the XAF application data source, and makes it difficult to use an arbitrary data service or a specialized database in this role.

Currently, XAF supports the XPO  and Entity Framework ORM libraries out of the box with the help of the XPObjectSpace/XPObjectSpaceProvider  and EFObjectSpace/EFObjectSpaceProvider APIs respectively. They allow connecting an XAF application directly to relational databases supported by these libraries. See the Database Engines Supported by XPO and Entity Framework Data Providers articles for more details.

Also, starting with version 16.1, we introduced the XAF Mobile (CTP) Application Platform. It exposes the XAF application database via the standard OData V3 service that can be consumed by the XAF mobile client, as well as by any custom client you may want to create. Refer to the FAQ: New XAF HTML5/JavaScript mobile UI (CTP) article for more details.

If data from any custom data source (even NoSQL) needs to be used in some XAF views (not all, because otherwise ROI from using XAF can be low), without replacing the main XAF application data store, non-persistent or POCO objects can be used to represent this data with the help of theNonPersistentObjectSpace/NonPersistentObjectSpaceProvider  APIs.  Non-persistent data is usually not queried from a database using your ORM data model, and this can be extremely helpful for analysis and reporting data obtained from dynamic runtime calculations, stored procedures, arbitrary SQL queries or third-party services. Also, such a non-persistent POCO class may be required if you want to display a standard XAF List or Detail View with temporary data generated in code or loaded from a custom storage; or display an empty View (dialog) and then process the user input. Refer to examples in the "Business Model Design - Non-Persistent Objects" part of the Task-Based Help topic for more details. Alternatively, you can display and manipulate any custom data with the help of non-XAF forms or fully custom user controls embedded into standard XAF views as described at eXpressApp Framework > Concepts > UI Construction > Using a Custom Control that is not Integrated by Default.

How to map ORM data model to another schema, e.g. other than the default "dbo" in MS SQL Server?

I just wanted to bring your attention to the recent update of one of the articles in our support knowledge, which is devoted to advanced data layer customizations - telling XAF business objects to use a different owner schema in the database.

Here we go:

How to customize the underlying database provider options and data access behavior in XAF

I just wanted to repost my recent update to the corresponding article, because this information can interest some advanced XAF users.

IMPORTANT NOTE

This article describes some advanced customization techniques and low-level entities of the framework with regard to data access, which may be required in complex scenarios only.
So, if you just want to change the connection string, e.g. to use the Oracle instead of the Microsoft SQL Server database, then you would better refer to the Connect an XAF Application to a Database Provider article and documentation on your database provider instead. The XAF integration of supported ORM libraries is also described in the Business Model Design section of the framework's documentation.

Introducing IObjectSpaceProvider and IObjectSpace

XAF accesses data from a data store through special abstractions called - IObjectSpaceProvider and IObjectSpace.
The IObjectSpace is an abstraction above the ORM-specific database context (e.g., the DBContext used in Entity Framework or the Session in XPO) allowing you to query or modify data.
The IObjectSpaceProvider is a provider/creator of IObjectSpace entities, which also manages which business types these IObjectSpace are supposed to work with, how to set up the underlying connection to the database, create and update it and other low level data access options.

An XafApplication can use one or several IObjectSpaceProvider objects at the same time, and you can access this information through the XafApplication.ObjectSpaceProvder or XafApplication.ObjectSpaceProviders properties. Check out these help links to learn more on how to plug in custom IObjectSpaceProvider objects a well.

There are several built-in implementations of the IObjectSpaceProvider and IObjectSpace interfaces in our framework, which are usually specific to a target ORM (Entity Framework or XPO). I suggest you check out the source code of the default framework classes to better understand the role of the IObjectSpaceProvider:

...\DevExpress.ExpressApp.Xpo\XPObjectSpaceProvider.cs
...\DevExpress.ExpressApp.EF\EFObjectSpaceProvider.cs