The requested page is not available for the requested platform. You are viewing the content for .NET Framework 4.5.2+ platform.
.NET Framework 4.5.2+
.NET Framework 4.5.2+
.NET Standard 2.0+

AggregatedAttribute Class

Indicates that persistent objects referenced by the target property are aggregated.

Namespace: DevExpress.Xpo

Assembly: DevExpress.Xpo.v19.2.dll

Declaration

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, Inherited = true)]
public sealed class AggregatedAttribute : Attribute
<AttributeUsage(AttributeTargets.Property Or AttributeTargets.Field, Inherited:=True)>
Public NotInheritable Class AggregatedAttribute
    Inherits Attribute
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, Inherited = true)]
public sealed class AggregatedAttribute : Attribute
<AttributeUsage(AttributeTargets.Field Or AttributeTargets.Property, Inherited:=True)>
Public NotInheritable Class AggregatedAttribute
    Inherits Attribute

Remarks

An aggregated object is a dependent object that is linked to its owner and cannot exist without its owner. When an owner is deleted, any aggregated objects it owns are deleted as well. All aggregated objects are saved automatically when the owner object is saved.

You can apply Xpo.AggregatedAttribute to an XPO reference property or to a collection property that participates in a relationship. If a collection property does not have the AssociationAttribute, that means it does not participate in a relationship, and Xpo.AggregatedAttribute has no effect on such a property.

Note

In XAF applications, use this attribute for XPO objects only. If you use Entity Framework or non-persistent objects, and need to mark properties as aggregated, apply the DC.AggregatedAttribute.

Examples

The following example demonstrates how to implement a one-to-many relationship between persistent objects, so that child objects are considered a part of their owner (when an owner is deleted, its aggregated objects will be automatically deleted; similarly, when an object is saved its aggregated objects will also be saved).

A one-to-many relationship is set up using the AssociationAttribute attribute. The AggregatedAttribute attribute is used to implement aggregation.

In this example, a Person object can have multiple addresses that are stored in the Person.Addresses collection. Each address in this collection is represented by an Address persistent class. The Person.Addresses property is marked with the AssociationAttribute and AggregatedAttribute attributes.

If you run the code below as is, the console output will be:

7654 Amsterdam Ave, New York, NY 555 Harbor Way, Santa Barbara, CA

If you remove the Aggregated attribute, the output will change to:

7654 Amsterdam Ave, New York, NY 7654 Amsterdam Ave, New York, NY

using System;
using System.Collections.Generic;
using System.Linq;
using DevExpress.Xpo;

namespace ConsoleApplication1 {
    public class Person : XPObject {
        public string Name {
            get { return fName; }
            set { SetPropertyValue(nameof(Name), ref fName, value); }
        }
        string fName;

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

    public class Address : XPObject {
        [Association("PersonAddresses")]
        public Person Owner {
            get { return fOwner; }
            set { SetPropertyValue(nameof(Owner), ref fOwner, value); }
        }
        Person fOwner;

        public string AddressInfo {
            get { return fAddressInfo; }
            set { SetPropertyValue(nameof(AddressInfo), ref fAddressInfo, value); }
        }
        string fAddressInfo;

    }

    class Program {
        static void Main(string[] args) {
            // Create a new instance of the Person class
            Person person = new Person() { Name = "Andrew Smith" };
            // Add an address for the person.
            Address address = new Address() { AddressInfo = "7654 Amsterdam Ave, New York, NY" };
            person.Addresses.Add(address);

            // Save the created Person object. The contents of the Addresses collection will be saved as well.
            person.Save();
            // Reload the object to verify if changes were saved.
            address.Reload();
            Console.WriteLine(address.AddressInfo);

            address.AddressInfo = "555 Harbor Way, Santa Barbara, CA";
            person.Save();
            // Reload the object to verify if changes were saved.
            address.Reload();
            Console.WriteLine(address.AddressInfo);

            Console.ReadKey();
        }
    }
}

Inheritance

Object
Attribute
AggregatedAttribute
See Also