IObjectSpace.FindObject(Type, CriteriaOperator) Method

Searches for the first object that matches the specified criteria and is of the specified type. The search takes uncommitted changes into account.

Namespace: DevExpress.ExpressApp

Assembly: DevExpress.ExpressApp.v23.2.dll

NuGet Package: DevExpress.ExpressApp

Declaration

C#

object FindObject(
    Type objectType,
    CriteriaOperator criteria
)

VB.NET

Function FindObject(
    objectType As Type,
    criteria As CriteriaOperator
) As Object

Parameters

Name	Type	Description
objectType	Type	A Type object which is the type of objects to search for.
criteria	CriteriaOperator	A CriteriaOperator descendant which is the criteria to match persistent objects.

Returns

Type	Description
Object	An object which is the first persistent object which matches the specified criteria. null (Nothing in Visual Basic) if there is no persistent object which matches the criteria.

Remarks

The following example uses a Parametrized Action to search for a Person by LastName, and then assigns all deferred tasks to that person.

C#

using System.Collections;
using DevExpress.Data.Filtering;
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Actions;
using DevExpress.Persistent.Base;
using DevExpress.Persistent.Base.General;
using DevExpress.Persistent.BaseImpl;
// ...
public class AssignTasksController : ObjectViewController<ListView, MainDemo.Module.BusinessObjects.DemoTask> {
    public AssignTasksController() {
        ParametrizedAction assignTasksAction = new ParametrizedAction(
            this, "AssignTasks", PredefinedCategory.Edit, typeof(string));
        assignTasksAction.Execute += AssignTasksAction_Execute;
    }
    private void AssignTasksAction_Execute(object sender, ParametrizedActionExecuteEventArgs e) {
        IObjectSpace objectSpace = View.ObjectSpace;
        string personParamValue = e.ParameterCurrentValue as string;
        CriteriaOperator personCriteria = CriteriaOperator.Parse("Contains([LastName], ?)", personParamValue);
        Person person = (Person)objectSpace.FindObject(typeof(Person), personCriteria);
        if(person != null) {
            CriteriaOperator taskCriteria = CriteriaOperator.Parse("[Status] = ?", TaskStatus.Deferred);
            IList tasks = objectSpace.GetObjects(
                typeof(MainDemo.Module.BusinessObjects.DemoTask), taskCriteria);
            foreach(MainDemo.Module.BusinessObjects.DemoTask task in tasks) {
                task.AssignedTo = person;
            }
        }
    }
}

VB.NET

Imports System.Collections
Imports DevExpress.Data.Filtering
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Actions
Imports DevExpress.Persistent.Base
Imports DevExpress.Persistent.Base.General
Imports DevExpress.Persistent.BaseImpl
' ...
Public Class AssignTasksController
    Inherits ObjectViewController(Of ListView, MainDemo.Module.BusinessObjects.DemoTask)

    Public Sub New()
        Dim assignTasksAction As New ParametrizedAction(Me, "AssignTasks", PredefinedCategory.Edit, GetType(String))
        AddHandler assignTasksAction.Execute, AddressOf AssignTasksAction_Execute
    End Sub
    Private Sub AssignTasksAction_Execute(ByVal sender As Object, ByVal e As ParametrizedActionExecuteEventArgs)
        Dim objectSpace As IObjectSpace = View.ObjectSpace
        Dim personParamValue As String = TryCast(e.ParameterCurrentValue, String)
        Dim personCriteria As CriteriaOperator = CriteriaOperator.Parse("Contains([LastName], ?)", personParamValue)
        Dim person As Person = CType(objectSpace.FindObject(GetType(Person), personCriteria), Person)
        If person IsNot Nothing Then
            Dim taskCriteria As CriteriaOperator = CriteriaOperator.Parse("[Status] = ?", TaskStatus.Deferred)
            Dim tasks As IList = objectSpace.GetObjects( _
                GetType(MainDemo.Module.BusinessObjects.DemoTask), taskCriteria)
            For Each task As MainDemo.Module.BusinessObjects.DemoTask In tasks
                task.AssignedTo = person
            Next task
        End If
    End Sub
End Class

When implementing the IObjectSpace interface in the BaseObjectSpace class’s descendant, you don’t have to implement the FindObject method. The BaseObjectSpace class’ FindObject(Type objectType, CriteriaOperator criteria) method invokes a public virtual FindObject(Type objectType, CriteriaOperator criteria, Boolean inTransaction) method passing true as the inTransaction parameter. So, to implement an object search, override the public virtual BaseObjectSpace.FindObject method.

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the FindObject(Type, CriteriaOperator) method.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

xaf-web-forms-use-oauth2-authentication-providers/CS/MySolution.Web/Security/OAuthProvider.cs#L29

if (userEmail != null) {
    user = (ApplicationUser)objectSpace.FindObject(userType, CriteriaOperator.Parse("OAuthAuthenticationEmails[Email = ?]", userEmail));
    if (user == null && CreateUserAutomatically) {

VB.NET

xaf-web-forms-use-oauth2-authentication-providers/VB/MySolution.Web/Security/OAuthProvider.vb#L31

If userEmail IsNot Nothing Then
    user = DirectCast(objectSpace.FindObject(userType, CriteriaOperator.Parse("OAuthAuthenticationEmails[Email = ?]", userEmail)), ApplicationUser)
    If user Is Nothing AndAlso CreateUserAutomatically Then