Reference Properties in XPO

• Nov 11, 2022
• 3 minutes to read

The example below illustrates how to implement Reference (Foreign Key, Complex Type) Properties in an XPO persistent class.

C#

private ReferencedObject lookupReferencedObject;
// Displayed in a lookup control:
public ReferencedObject LookupReferencedObject {
    get { return lookupReferencedObject; }
    set { SetPropertyValue(nameof(LookupReferencedObject), ref lookupReferencedObject, value); }
}

private ExpandPropertiesObject expandPropertiesObject;
// Displayed in a set of editors. Each editor represents an individual property of the referenced object:
[Aggregated, ExpandObjectMembers(ExpandObjectMembers.Always)]
public ExpandPropertiesObject ExpandPropertiesObject {
    get { return expandPropertiesObject; }
    set { SetPropertyValue(nameof(ExpandPropertiesObject), ref expandPropertiesObject, value); }
}

private EmbeddedDetailViewObject embeddedDetailViewObject;
// Displayed in a Detail Property Editor that shows a referenced object's Detail View:
[Aggregated, EditorAlias(EditorAliases.DetailPropertyEditor), ExpandObjectMembers(ExpandObjectMembers.Never)]
public EmbeddedDetailViewObject EmbeddedDetailViewObject {
    get { return embeddedDetailViewObject; }
    set { SetPropertyValue(nameof(EmbeddedDetailViewObject), ref embeddedDetailViewObject, value); }
}

private PopupDetailViewObject popupDetailViewObject;
// Displayed in a button edit that invokes a referenced object's Detail View in a separate modal window:
[Aggregated, ExpandObjectMembers(ExpandObjectMembers.Never)]
public PopupDetailViewObject PopupDetailViewObject {
    get { return popupDetailViewObject; }
    set { SetPropertyValue(nameof(PopupDetailViewObject), ref popupDetailViewObject, value); }
}

VB.NET

Private _lookupReferencedObject As ReferencedObject
' Displayed in a lookup control:
Public Property LookupReferencedObject() As ReferencedObject
    Get
        Return _lookupReferencedObject
    End Get
    Set(ByVal value As ReferencedObject)
        SetPropertyValue(NameOf(LookupReferencedObject), _lookupReferencedObject, value)
    End Set
End Property

Private _expandPropertiesObject As ExpandPropertiesObject
' Displayed in a set of editors. Each editor represents an individual property of the referenced object:
<Aggregated, ExpandObjectMembers(ExpandObjectMembers.Always)>
Public Property ExpandPropertiesObject() As ExpandPropertiesObject
    Get
        Return _expandPropertiesObject
    End Get
    Set(ByVal value As ExpandPropertiesObject)
        SetPropertyValue(NameOf(ExpandPropertiesObject), _expandPropertiesObject, value)
    End Set
End Property

Private _embeddedDetailViewObject As EmbeddedDetailViewObject
' Displayed in a Detail Property Editor that shows a referenced object's Detail View:
<Aggregated, EditorAlias(EditorAliases.DetailPropertyEditor), ExpandObjectMembers(ExpandObjectMembers.Never)>
Public Property EmbeddedDetailViewObject() As EmbeddedDetailViewObject
    Get
        Return _embeddedDetailViewObject
    End Get
    Set(ByVal value As EmbeddedDetailViewObject)
        SetPropertyValue(NameOf(EmbeddedDetailViewObject), _embeddedDetailViewObject, value)
    End Set
End Property

Private _popupDetailViewObject As PopupDetailViewObject
' Displayed in a button edit that invokes a referenced object's Detail View in a separate modal window:
<Aggregated, ExpandObjectMembers(ExpandObjectMembers.Never)>
Public Property PopupDetailViewObject() As PopupDetailViewObject
    Get
        Return _popupDetailViewObject
    End Get
    Set(ByVal value As PopupDetailViewObject)
        SetPropertyValue(NameOf(PopupDetailViewObject), _popupDetailViewObject, value)
    End Set
End Property

If you use Detail Property Editor for a reference property, or apply ExpandObjectMembers attribute to a reference property, it is required to initialize such a property in the when a new parent object is created. Otherwise, the reference property’s fields will be read-only. The initialization should be done in the overridden AfterConstruction method the following way:

C#

public override void AfterConstruction() {
    base.AfterConstruction();
    embeddedDetailViewObject = new EmbeddedDetailViewObject(Session);
}

VB.NET

Public Overrides Sub AfterConstruction()
    MyBase.AfterConstruction()
    embeddedDetailViewObject = New EmbeddedDetailViewObject(Session)
End Sub