Session.PreFetchAsync(IEnumerable, XPMemberInfo, IEnumerable, CancellationToken) Method

Asynchronously forces associated collection data loading for specified parent objects.

Namespace: DevExpress.Xpo

Assembly: DevExpress.Xpo.v23.2.dll

NuGet Packages: DevExpress.Win.PivotGrid, DevExpress.Win.TreeMap, DevExpress.Xpo

NuGet Package: DevExpress.Xpo

Declaration

C#

public Task PreFetchAsync(
    IEnumerable objects,
    XPMemberInfo collectionInObjects,
    IEnumerable collectionsContent,
    CancellationToken cancellationToken = default(CancellationToken)
)

VB.NET

Public Function PreFetchAsync(
    objects As IEnumerable,
    collectionInObjects As XPMemberInfo,
    collectionsContent As IEnumerable,
    cancellationToken As CancellationToken = Nothing
) As Task

Parameters

Name	Type	Description
objects	IEnumerable	An IEnumerable list of parent objects.
collectionInObjects	XPMemberInfo	An XPMemberInfo object that contains metadata information. This data specifies associated collection data to be retrieved.
collectionsContent	IEnumerable	An IEnumerable list of the collection’s content. If the collectionInObjects data was previously loaded, you can avoid reloading it by passing the loaded data to the collectionsContent parameter. Note that if this parameter does not contain a part of the collection’s content, this part will not be loaded from a database.

Optional Parameters

Name	Type	Default	Description
cancellationToken	CancellationToken	null	A CancellationToken object that delivers a cancellation notice to the running operation.

Returns

Type	Description
Task	A Task that forces associated collection data loading for specified parent objects.

Remarks

By default, data is loaded automatically when you access a persistent object’s nested collection for the first time. The PreFetchAsync loads all associated collection data for specified parent objects, before these collections are accessed. No additional SQL queries for this data will be performed later.

C#

using System.Threading;
using DevExpress.Xpo;
using DevExpress.Xpo.Metadata;
// ...
CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
CancellationToken cancellationToken = cancellationTokenSource.Token;
XPCollection<Person> people = new XPCollection<Person>(session);
XPMemberInfo phoneNumbersInfo = session.GetClassInfo(typeof(Person)).GetMember(nameof(PhoneNumbers));
XPCollection<PhoneNumber> phoneNumbers = new XPCollection<PhoneNumber>(session);
await session.PreFetchAsync(people, phoneNumbersInfo, phoneNumbers, cancellationToken);

VB.NET

Imports System.Threading
Imports DevExpress.Xpo
Imports DevExpress.Xpo.Metadata
' ...
Private cancellationTokenSource As New CancellationTokenSource()
Private cancellationToken As CancellationToken = cancellationTokenSource.Token
Private people As New XPCollection(Of Person)(session)
Private phoneNumbersInfo As XPMemberInfo = session.GetClassInfo(GetType(Person)).GetMember(NameOf(PhoneNumbers))
Private phoneNumbers As New XPCollection(Of PhoneNumber)(session)
Await session.PreFetchAsync(people, phoneNumbersInfo, phoneNumbers, cancellationToken)