XPObjectSpace.FindObjectAsync<ObjectType>(CriteriaOperator, CancellationToken) Method

Asynchronously searches for an object that matches the specified criteria. This object’s type is designated by the specified generic parameter.

Namespace: DevExpress.ExpressApp.Xpo

Assembly: DevExpress.ExpressApp.Xpo.v25.2.dll

NuGet Package: DevExpress.ExpressApp.Xpo

Declaration

C#

public Task<ObjectType> FindObjectAsync<ObjectType>(
    CriteriaOperator criteria,
    CancellationToken cancellationToken = default(CancellationToken)
)

VB.NET

Public Function FindObjectAsync(Of ObjectType)(
    criteria As CriteriaOperator,
    cancellationToken As CancellationToken = Nothing
) As Task(Of ObjectType)

Parameters

Name	Type	Description
criteria	CriteriaOperator	A CriteriaOperator descendant which represents the criteria the persistent object must match.

Optional Parameters

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

Type Parameters

Name	Description
ObjectType	A type of objects to search for.

Returns

Type	Description
Task<ObjectType>	A Task that returns an object. This object represents a persistent object that matches the specified criteria. null if no persistent object is found that matches the criteria.

Remarks

The following code snippet uses 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, XAF displays a Detail View for a new Contact object.

C#

using DevExpress.Data.Filtering;
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 obj = await contactObjectSpace.FindObjectAsync<Contact>(
                    CriteriaOperator.Parse(string.Format("[Oid] = '{0}'", assignedTo.Oid)), 
                    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;
    }
}

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.

Implements

FindObjectAsync<ObjectType>(CriteriaOperator, CancellationToken)