How to: Use Both Entity Framework and XPO in a Single Application

• Feb 25, 2022
• 5 minutes to read

This topic demonstrates how to create a simple XAF application that uses both the Entity Framework (EF) and eXpress Persistent Objects (XPO) business models. For instance, this approach is required if you want to reuse the Entity Framework model from a non-XAF application in your existing XPO-based XAF project. As a result, your application will access two databases, the first one using XPO and the second using EF.

Note

• This topic demonstrates the code that can be generated automatically by the Solution Wizard. Proceed, if you want to implement the demonstrated functionality in the existing XAF solution. If you are creating a new XAF solution, use the wizard instead. You can choose both EF and XPO in the Choose ORM page of the wizard (Entity Framework Code First plus eXpress Persistent Objects).
• Mobile applications do not support the EF business model.

Tip

A complete sample project is available in the DevExpress Code Examples database at How to: Use both Entity Framework and XPO in a Single Application.

Add an EF Data Model in Code

• Reference the EntityFramework.dll and EntityFramework.SqlServer.dll assemblies. You can use NuGet to download and reference these assemblies automatically (see Get Entity Framework). The supported Entity Framework version is 6.
• Reference the DevExpress.ExpressApp.EF.v19.2.dll assembly, which provides Entity Framework support in XAF.

• In the module project, implement the following EntityFrameworkSampleObject and MyDbContext classes (learn more about Entity Framework Code First in XAF).

  C#

  using System.ComponentModel;
  using EntityFramework.dll;
  using DevExpress.Persistent.Base;
  using DevExpress.ExpressApp.DC;
  // ...
  [DefaultClassOptions]
  public class EntityFrameworkSampleObject {
      [Browsable(false)]
      public int Id { get; protected set; }
      public string Name { get; set; }
      [FieldSize(FieldSizeAttribute.Unlimited)]
      public String Description { get; set; }
  }
  public class MyDbContext : DbContext {
      public MyDbContext(string connectionString) : base(connectionString) { }
      public DbSet<EntityFrameworkSampleObject> SampleObjects { get; set; }
  }
  

  VB.NET

  Imports System.ComponentModel
  Imports EntityFramework
  Imports DevExpress.ExpressApp.DC
  ' ...
  <DefaultClassOptions> _
  Public Class EntityFrameworkSampleObject
      Private privateId As Integer
      <Browsable(False)> _
      Public Property Id() As Integer
          Get
              Return privateId
          End Get
          Protected Set(ByVal value As Integer)
              privateId = value
          End Set
      End Property
      Private privateName As String
      Public Property Name() As String
          Get
              Return privateName
          End Get
          Set(ByVal value As String)
              privateName = value
          End Set
      End Property
      Private privateDescription As String
      <FieldSize(FieldSizeAttribute.Unlimited)> _
      Public Property Description() As String
          Get
              Return privateDescription
          End Get
          Set(ByVal value As String)
              privateDescription = value
          End Set
      End Property
  End Class
  Public Class MyDbContext
      Inherits DbContext
  
      Public Sub New(ByVal connectionString As String)
          MyBase.New(connectionString)
      End Sub
      Private privateSampleObjects As DbSet(Of EntityFrameworkSampleObject)
      Public Property SampleObjects() As DbSet(Of EntityFrameworkSampleObject)
          Get
              Return privateSampleObjects
          End Get
          Set(ByVal value As DbSet(Of EntityFrameworkSampleObject))
              privateSampleObjects = value
          End Set
      End Property
  End Class
  

Add an XPO Data Model in Code

In the module project, implement the following BaseObject descendant.

C#

using DevExpress.Xpo;
using DevExpress.Persistent.Base;
using DevExpress.Persistent.BaseImpl;
using DevExpress.ExpressApp.DC;
// ...
[DefaultClassOptions]
public class XpoSampleObject : BaseObject {
    public XpoSampleObject(Session session) : base(session) { }
    private string name;
    public string Name {
        get { return name; }
        set { SetPropertyValue(nameof(Name), ref name, value); }
    }
    private string description;
    [Size(SizeAttribute.Unlimited)]
    public String Description { 
        get {return description; }
        set { SetPropertyValue(nameof(Description), ref description, value); }
    }
}

VB.NET

Imports DevExpress.Xpo
Imports DevExpress.Persistent.Base
Imports DevExpress.Persistent.BaseImpl
Imports DevExpress.ExpressApp.DC
' ...
<DefaultClassOptions> _
Public Class XpoSampleObject
    Inherits BaseObject

    Public Sub New(ByVal session As Session)
        MyBase.New(session)
    End Sub
    Private _name As String
    Public Property Name() As String
        Get
            Return _name
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(Name), _name, value)
        End Set
    End Property
    Private _description As String
    <Size(SizeAttribute.Unlimited)> _
    Public Property Description() As String
        Get
            Return _description
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(Description), _description, value)
        End Set
    End Property
End Class

Populate the DefaultObjectSpaceProviders Collection

By default, the CreateDefaultObjectSpaceProvider method implemented in the WinApplication.cs (WinApplication.vb) and WebApplication.cs (WebApplication.vb) files assigns an XPObjectSpaceProvider instance to the ObjectSpaceProvider parameter. Instead, you can add multiple Object Space Providers to the ObjectSpaceProviders parameter. XAF will automatically determine what Object Space Provider should be used to create an Object Space for each particular business object type. Modify the default implementation of the CreateDefaultObjectSpaceProvider method for both Windows Forms and ASP.NET application projects in the following manner.

C#

using DevExpress.ExpressApp.DC;
using DevExpress.ExpressApp.EF;
// ...
protected override void CreateDefaultObjectSpaceProvider(CreateCustomObjectSpaceProviderEventArgs args) {
    args.ObjectSpaceProviders.Add(
        new XPObjectSpaceProvider(ConfigurationManager.ConnectionStrings["ConnectionStringXpo"].ConnectionString, null));
    args.ObjectSpaceProviders.Add(
        new EFObjectSpaceProvider(typeof(MyDbContext),
        ConfigurationManager.ConnectionStrings["ConnectionStringEF"].ConnectionString));
}

VB.NET

Imports DevExpress.ExpressApp.DC
Imports DevExpress.ExpressApp.EF
' ...
Protected Overrides Sub CreateDefaultObjectSpaceProvider( _
ByVal args As CreateCustomObjectSpaceProviderEventArgs)
    args.ObjectSpaceProviders.Add(New XPObjectSpaceProvider( _
    ConfigurationManager.ConnectionStrings("ConnectionStringXpo").ConnectionString, Nothing))
    args.ObjectSpaceProviders.Add(New EFObjectSpaceProvider(GetType(MyDbContext), _
    ConfigurationManager.ConnectionStrings("ConnectionStringEF").ConnectionString))
End Sub

XAF uses the first registered Object Space Provider for the following purposes:

• to get XafApplication.ObjectSpaceProvider and XafApplication.ConnectionString property values;
• to pass this Provider as the CustomCheckCompatibilityEventArgs‘s ObjectSpaceProvider argument;
• to update an application.

Ensure that NonPersistentObjectSpaceProvider is not the first registered Provider in your application.

Specify Connection Strings for EF and XPO

The code in the previous section reads connection strings for each Object Space Provider from the configuration file (App.config in a Windows Forms application project and Web.config in ASP.NET), so specify the ConnectionStringXpo and ConnectionStringEF connection strings in both files.

XML

<connectionStrings>
    <add name="ConnectionStringXpo" connectionString="Integrated Security=SSPI;
    Pooling=false;Data Source=(local);Initial Catalog=MultipleORMsExampleXpo" />
    <add name="ConnectionStringEF" connectionString="Integrated Security=SSPI;
    Data Source=(local);Initial Catalog=MultipleORMsExampleEF" />
</connectionStrings>

Run the Application

Now you can run the application (Windows Forms or ASP.NET) to see that both EF and XPO objects are accessible.

Tip

If you want to create an Object Space in code when several Object Space providers are registered, use the overload of XafApplication.CreateObjectSpace method that takes the objectType parameter. In this instance, an Object Space that supports a particular object type will be created.

Note

When multiple Object Space Providers are registered in the XafApplication.ObjectSpaceProviders property, the ModuleUpdater.UpdateDatabaseAfterUpdateSchema method is executed multiple times, once for each registered Provider. In this method, before accessing an object of a particular type, check if the current Object Space supports this type using the IObjectSpace.CanInstantiate method.