Object Space

• Jun 11, 2021
• 3 minutes to read

In XAF applications, all data-aware manipulations are performed via the Object Space. The Object Space is an abstraction on the database context. The Object Space allows you to query or edit data in the transaction. Object Space is an ORM-independent implementation of the well-known Repository and Unit Of Work design patterns.

Object Space members are declared in the IObjectSpace interface. The BaseObjectSpace and CompositeObjectSpace classes implement the common code. XAF includes the following CompositeObjectSpace descendants:

• XPObjectSpace - used to access data via a Session when the XPO data model is used.
• EFObjectSpace - used to access data via a DbContext when the Entity Framework 6 data model is used;
• EFCoreObjectSpace - used to access data via a DbContext when the Entity Framework Core data model is used;
• NonPersistentObjectSpace - used to manage non-persistent objects that are not mapped to the database.

In most cases, you will access Object Space via the IObjectSpace interface and do not need to use these classes directly.

The following example demonstrates how to use Object Space methods:

C#

using DevExpress.Data.Filtering;
using DevExpress.ExpressApp;
using DevExpress.Persistent.BaseImpl;
using System;
using System.Collections.Generic;
using System.Linq;

//...
public void MethodInsideController(IObjectSpace objectSpace) {
    // In a ViewController, you can use the View.ObjectSpace property to access the current Object Space
    // or call the Application.CreateObjectSpace method to create a new Object Space.
    Person person = objectSpace.FirstOrDefault<Person>(p => p.FirstName == "John" && p.LastName == "Doe");
    if(person != null) {
        // IList<Task> outdatedTasks = objectSpace.GetObjects<Task>(CriteriaOperator.Parse("DueDate < ?", DateTime.Now));
        IQueryable<Task> outdatedTasks = objectSpace.GetObjectsQuery<Task>().Where(t => t.DueDate < DateTime.Now);
        foreach(Task task in outdatedTasks) {
            task.AssignedTo = person;
        }
    }
    objectSpace.CommitChanges();
}
//...

VB.NET

Imports DevExpress.Data.Filtering
Imports DevExpress.ExpressApp
Imports DevExpress.Persistent.BaseImpl
Imports System
Imports System.Collections.Generic
Imports System.Linq

'...
Public Sub MethodInsideController(ByVal objectSpace As IObjectSpace)
    ' In a ViewController, you can use the View.ObjectSpace property to access the current Object Space
    ' or call the Application.CreateObjectSpace method to create a new Object Space.
    Dim person As Person = objectSpace.FirstOrDefault(Of Person)(Function(p) p.FirstName = "John" AndAlso p.LastName = "Doe")
    If person IsNot Nothing Then
        ' Dim outdatedTasks As IList(Of Task) = objectSpace.GetObjects(Of Task)(CriteriaOperator.Parse("DueDate < ?", DateTime.Now))
        Dim outdatedTasks As IQueryable(Of Task) = objectSpace.GetObjectsQuery(Of Task)().Where(Function(t) t.DueDate < DateTime.Now)
        For Each task As Task In outdatedTasks
            task.AssignedTo = person
        Next
    End If

    objectSpace.CommitChanges()
End Sub
'...

For more information on ways to access an Object Space in different scenarios, refer to the following help topic: Ways to Implement Business Logic. To learn about Object Space API, see Create, Read, Update and Delete Data.