IObjectSpace.FindObject<ObjectType>(CriteriaOperator, Boolean) Method

Searches for the first object that matches the specified criteria. The object’s type is designated by the specified generic type parameter.

Namespace: DevExpress.ExpressApp

Assembly: DevExpress.ExpressApp.v23.2.dll

NuGet Package: DevExpress.ExpressApp

Declaration

C#

ObjectType FindObject<ObjectType>(
    CriteriaOperator criteria,
    bool inTransaction
)

VB.NET

Function FindObject(Of ObjectType)(
    criteria As CriteriaOperator,
    inTransaction As Boolean
) As ObjectType

Parameters

Name	Type	Description
criteria	CriteriaOperator	A CriteriaOperator descendant which is the criteria for matching persistent objects.
inTransaction	Boolean	true, if the filter takes unsaved changes into account; otherwise, false.

Type Parameters

Name	Description
ObjectType	The Type of objects that are retrieved.

Returns

Type	Description
ObjectType	An object which is the first persistent object which matches the specified 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 = objectSpace.FindObject<Person>(personCriteria, true);
        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 = objectSpace.FindObject(Of Person)(personCriteria, True)
        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<ObjectType> method. The BaseObjectSpace class’ FintObject<ObjectType>(CriteriaOperator criteria, Boolean inTransaction) method invokes a public virtual FindObject(Type objectType, CriteriaOperator criteria, Boolean inTransaction) method. So, you should only override the public virtual BaseObjectSpace.FindObject method to implement an object search.