IObjectSpaceAsync.GetObjectByKeyAsync(Type, Object, CancellationToken) Method

Returns the persistent object that has the specified value for its key property.

Namespace: DevExpress.ExpressApp

Assembly: DevExpress.ExpressApp.v24.1.dll

NuGet Package: DevExpress.ExpressApp

Declaration

C#

Task<object> GetObjectByKeyAsync(
    Type objectType,
    object key,
    CancellationToken cancellationToken = default(CancellationToken)
)

VB.NET

Function GetObjectByKeyAsync(
    objectType As Type,
    key As Object,
    cancellationToken As CancellationToken = Nothing
) As Task(Of Object)

Parameters

Name	Type	Description
objectType	Type	A Type object that is the type of objects to search for.
key	Object	An object that is the persistent object’s key property value.

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<Object>	A Task that returns the searched object. null (Nothing in Visual Basic) if no persistent object is found with the specified key.

Remarks

The GetObjectByKeyAsync method searches the memory for the object that has the specified value for its key property. If such an object is found, it is not reloaded from the database. Otherwise, the object is retrieved from the database.

To get the key property value, use the GetKeyValue(Object) method.

The following code demonstrates how you can use this method in a View Controller to find and show a Contact the selected DemoTask is assigned to. If this DemoTask is not assigned to any Contact, a Detail View for a new Contact object is shown.

C#

using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Actions;
using DevExpress.ExpressApp.Xpo;
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 assignedTo = (Contact)ViewCurrentObject.AssignedTo;
            if (assignedTo != null) {
                object key = ObjectSpace.GetKeyValue(assignedTo);
                object obj = await contactObjectSpace.GetObjectByKeyAsync(typeof(Contact), key,
                    cancellationTokenSource.Token);
                contactView.CurrentObject = obj ?? contactObjectSpace.CreateObject(typeof(Contact));
            }
            else {
                contactView.CurrentObject = contactObjectSpace.CreateObject(typeof(Contact));
            }
        if (contactObjectSpace.IsNewObject(contactView.CurrentObject)) {
            contactObjectSpace.Committed += contactObjectSpace_Committed;
        }
    }
    private void contactObjectSpace_Committed(object sender, EventArgs e) {
        ViewCurrentObject.AssignedTo = ObjectSpace.GetObject(contactView.CurrentObject) as Contact;
    }
}

VB.NET

Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Actions
Imports DevExpress.ExpressApp.Xpo
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 assignedTo As Contact = CType(ViewCurrentObject.AssignedTo, Contact)
        If assignedTo IsNot Nothing Then
            Dim key As Object = ObjectSpace.GetKeyValue(assignedTo)
            Dim obj As Object = Await contactObjectSpace.GetObjectByKeyAsync(GetType(Contact), _
                key, cancellationTokenSource.Token)
            contactView.CurrentObject = If(obj, contactObjectSpace.CreateObject(GetType(Contact)))
        Else
            contactView.CurrentObject = contactObjectSpace.CreateObject(GetType(Contact))
        End If
        If contactObjectSpace.IsNewObject(contactView.CurrentObject) Then
            AddHandler contactObjectSpace.Committed, AddressOf contactObjectSpace_Committed
        End If
    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.