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.NET 6.0+

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

Asynchronously searches for an object that matches the specified criteria. The specified generic parameter determines the object’s type.

Namespace: DevExpress.ExpressApp

Assembly: DevExpress.ExpressApp.v24.1.dll

NuGet Package: DevExpress.ExpressApp

Declaration

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

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 (Nothing in Visual Basic) if no persistent object is found that matches the criteria.

Remarks

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.

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.

See Also