Base Persistent Classes

• May 17, 2023
• 2 minutes to read

This topic describes the base persistent classes that can be used in XAF applications when creating a data model with XPO.

The following table lists the base persistent classes you can inherit from when you define persistent business classes:

Persistent Class	Namespace	Supported Concurrency Control	Contains the Auto-Generated Primary Key Property	Supports Deferred Deletion
XPLiteObject	DevExpress.Xpo	None (“Last in wins”)	No	No
XPBaseObject	DevExpress.Xpo	Optimistic	No	No
XPCustomObject	DevExpress.Xpo	Optimistic	No	Yes
XPObject	DevExpress.Xpo	Optimistic	Yes. Integer type.	Yes
BaseObject	DevExpress.Persistent.BaseImpl	Optimistic	Yes. Guid type.	Yes

The BaseObject class is used when creating business classes from the XPO Business Object template. It is a feature-rich persistent class that supports the optimistic concurrency control (optimistic locking mechanism).

We recommend using the XPObject class if your business class should use the integer type primary key. This class also supports optimistic concurrency control.

You need to define the primary key property in the business class declaration if you are using classes which do not have the auto-generated primary key property. The following code snippet illustrates this:

C#

using System.ComponentModel;
using DevExpress.Persistent.Base;
using DevExpress.Xpo;
//...
[DefaultClassOptions]
public class MyClass : XPLiteObject {
    public MyClass(Session session) : base(session) { }
    [Key(AutoGenerate = true), Browsable(false)]
    public int Oid { get; set; }
    string fMyProperty;
    public string MyProperty {
        get { return fMyProperty; }
        set { SetPropertyValue(nameof(MyProperty), ref fMyProperty, value); }
    }
}

VB.NET

Imports System.ComponentModel
Imports DevExpress.Persistent.Base
Imports DevExpress.Xpo
'...
<DefaultClassOptions>
Public Class [MyClass]
    Inherits XPLiteObject
    Public Sub New(ByVal session As Session)
        MyBase.New(session)
    End Sub
    <Key(AutoGenerate:=True)>
    <Browsable(False)>
    Public Property Oid() As Integer
    Private fMyProperty As String
    Public Property MyProperty() As String
        Get
            Return fMyProperty
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(MyProperty), fMyProperty, value)
        End Set
    End Property
End Class

If you need to consider whether to use a base class that supports the deferred deletion feature, refer to the XPO documentation: Deleting Persistent Objects.

You can implement a custom base persistent class. To learn more, refer to the How to: Implement a Custom Base Persistent Class help topic.