Session.PreFetchAsync<T>(IEnumerable<T>, String, IEnumerable, CancellationToken) Method

Asynchronously forces associated collection data loading for specified parent objects.

Namespace: DevExpress.Xpo

Assembly: DevExpress.Xpo.v19.2.dll

Declaration

C#

public Task PreFetchAsync<T>(
    IEnumerable<T> objects,
    string collectionInObjects,
    IEnumerable collectionsContent,
    CancellationToken cancellationToken
)

VB.NET

Public Function PreFetchAsync(Of T)(
    objects As IEnumerable(Of T),
    collectionInObjects As String,
    collectionsContent As IEnumerable,
    cancellationToken As CancellationToken
) As Task

Parameters

Name	Type	Description
objects	IEnumerable<T>	An IEnumerable list of parent objects.
collectionInObjects	String	A string which is the name of the associated collection property.
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.
cancellationToken	CancellationToken	A CancellationToken object that delivers a cancellation notice to the running operation.

Type Parameters

Name
T

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 nested collection for the first time. The PreFetchAsync<T> method loads required associated collection data for a parent object at once. No additional SQL queries for this data will be performed later.

C#

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

VB.NET

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