How to: Create an Aggregated Object

• Nov 21, 2018
• 2 minutes to read

An aggregated object is considered a part of the owning object and cannot exist separately. When the owner is deleted, aggregated objects must be deleted as well. XPO can handle aggregated object deletion automatically. To do this, use the AggregatedAttribute to specify links to aggregated objects. In the following code example, the DefaultAddress and Addresses properties are considered to be a natural part of the Person objects, so we mark these properties as aggregated.

C#

public class Address : XPObject {
    // For brevity, we omitted the declaration of constructors
    // and fields corresponding to persistent properties.
    // ...
    public string City;
    public string Street;

    [Association("PersonAddresses")]
    public Person Owner;
}

public class Person : XPObject {
    // For brevity, we omitted the declaration of constructors
    // and fields corresponding to persistent properties.
    // ...
    public override void AfterConstruction() {
        base.AfterConstruction();
        DefaultAddress = new Address(Session);
    }

    [Aggregated]
    public Address DefaultAddress;

    [Aggregated, Association("PersonAddresses")]
    public XPCollection<Address> Addresses {
        get { return GetCollection<Address>("Addresses"); }
    }
}

VB.NET

Public Class Address
    Inherits XPObject
    ' For brevity, we omitted the declaration of constructors
    ' and fields corresponding to persistent properties.
    ' ...
    Public City As String
    Public Street As String

    <Association("PersonAddresses")> _
    Public Owner As Person
End Class

Public Class Person
vInherits XPObject
    ' For brevity, we omitted the declaration of constructors
    ' and fields corresponding to persistent properties.
    ' ...
    Public Overrides Sub AfterConstruction()
        MyBase.AfterConstruction()
        DefaultAddress = New Address(Session)
    End Sub

    <Aggregated> _
    Public DefaultAddress As Address

    <Aggregated, Association("PersonAddresses")> _
    Public ReadOnly Property Addresses() As XPCollection(Of Address)
        Get
            Return GetCollection(Of Address)("Addresses")
        End Get
    End Property
End Class

Note

We did not mark the Address class as aggregated, because the aggregation is an attribute of an object association and is not a class in itself.