XPObjectSpace.PreFetchAsync(Object, String[], CancellationToken) Method
Asynchronously forces associated collection data loading and delayed property loading for specified parent objects.
Namespace: DevExpress.ExpressApp.Xpo
Assembly:
DevExpress.ExpressApp.Xpo.v19.2.dll
Declaration
public Task PreFetchAsync(
object collection,
string[] propertyNames,
CancellationToken cancellationToken = null
)
Public Function PreFetchAsync(
collection As Object,
propertyNames As String(),
cancellationToken As CancellationToken = Nothing
) As Task
public Task PreFetchAsync(
object collection,
string[] propertyNames,
CancellationToken cancellationToken = default(CancellationToken)
)
Public Function PreFetchAsync(
collection As Object,
propertyNames As String(),
cancellationToken As CancellationToken = Nothing
) As Task
Parameters
| Name |
Type |
Description |
| collection |
Object |
A collection of parent objects.
|
| propertyNames |
String[] |
An array of strings which are the names of the associated collection properties or delayed properties.
|
Optional Parameters
Returns
The following code demonstrates how you can use this method in a WinForms-specific View Controller.
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Actions;
using DevExpress.ExpressApp.Xpo;
using MainDemo.Module.BusinessObjects;
using System;
using System.Threading;
// ...
public class AsyncAssignedToInfoController : ObjectViewController<ListView, DemoTask> {
View contactView = null;
public AsyncAssignedToInfoController() : base() {
SimpleAction showAssignedToInfoAction = new SimpleAction(this, "Assigned contact's info", "Edit");
showAssignedToInfoAction.SelectionDependencyType = SelectionDependencyType.RequireSingleObject;
showAssignedToInfoAction.Execute += showAssignedToInfoAction_Execute;
}
async private void showAssignedToInfoAction_Execute(object sender, SimpleActionExecuteEventArgs e) {
CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
XPObjectSpace contactObjectSpace = (XPObjectSpace)Application.CreateObjectSpace(typeof(Contact));
contactView = Application.CreateDetailView(contactObjectSpace, "Contact_DetailView", true);
e.ShowViewParameters.CreatedView = contactView;
Contact obj = null;
if (ViewCurrentObject.AssignedTo != null) {
obj = (Contact)await contactObjectSpace.GetObjectAsync(ViewCurrentObject.AssignedTo);
Contact[] contacts = new Contact[] { obj };
await contactObjectSpace.PreFetchAsync(contacts, new string[] { "Tasks" });
}
if (obj == null) {
obj = contactObjectSpace.CreateObject<Contact>();
contactObjectSpace.Committed += contactObjectSpace_Committed;
}
contactView.CurrentObject = obj;
}
private void contactObjectSpace_Committed(object sender, EventArgs e) {
ViewCurrentObject.AssignedTo = ObjectSpace.GetObject(contactView.CurrentObject) as Contact;
}
}
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Actions
Imports DevExpress.ExpressApp.Xpo
Imports MainDemo.Module.BusinessObjects
Imports System
Imports System.Threading
' ...
Public Class AsyncAssignedToInfoController
Inherits ObjectViewController(Of ListView, DemoTask)
Private contactView As View = Nothing
Public Sub New()
MyBase.New()
Dim showAssignedToInfoAction As New SimpleAction(Me, "Assigned contact's info", "Edit")
showAssignedToInfoAction.SelectionDependencyType = SelectionDependencyType.RequireSingleObject
AddHandler showAssignedToInfoAction.Execute, AddressOf showAssignedToInfoAction_Execute
End Sub
Private Async Sub showAssignedToInfoAction_Execute(ByVal sender As Object, ByVal e As SimpleActionExecuteEventArgs)
Dim cancellationTokenSource As New CancellationTokenSource()
Dim contactObjectSpace As XPObjectSpace = CType(Application.CreateObjectSpace(GetType(Contact)), XPObjectSpace)
contactView = Application.CreateDetailView(contactObjectSpace, "Contact_DetailView", True)
e.ShowViewParameters.CreatedView = contactView
Dim obj As Contact = Nothing
If ViewCurrentObject.AssignedTo IsNot Nothing Then
obj = CType(Await contactObjectSpace.GetObjectAsync(ViewCurrentObject.AssignedTo), Contact)
Dim contacts() As Contact = {obj}
Await contactObjectSpace.PreFetchAsync(contacts, New String() {"Tasks"})
End If
If obj Is Nothing Then
obj = contactObjectSpace.CreateObject(Of Contact)()
AddHandler contactObjectSpace.Committed, AddressOf contactObjectSpace_Committed
End If
contactView.CurrentObject = obj
End Sub
Private Sub contactObjectSpace_Committed(ByVal sender As Object, ByVal e As EventArgs)
ViewCurrentObject.AssignedTo = TryCast(ObjectSpace.GetObject(contactView.CurrentObject), Contact)
End Sub
End Class
In the current example, the cancellationToken parameter is used for demonstration purposes. You can skip it or use to cancel an asynchronous operation as shown in the CancellationToken topic.
See Also