Session.FindObjectAsync(PersistentCriteriaEvaluationBehavior, Type, CriteriaOperator, CancellationToken) Method

Asynchronously searches for the first object that matches the specified criteria.

Namespace: DevExpress.Xpo

Assembly: DevExpress.Xpo.v24.2.dll

Declaration

C#

public Task<object> FindObjectAsync(
    PersistentCriteriaEvaluationBehavior criteriaEvaluationBehavior,
    Type objType,
    CriteriaOperator criteria,
    CancellationToken cancellationToken = default(CancellationToken)
)

VB.NET

Public Function FindObjectAsync(
    criteriaEvaluationBehavior As PersistentCriteriaEvaluationBehavior,
    objType As Type,
    criteria As CriteriaOperator,
    cancellationToken As CancellationToken = Nothing
) As Task(Of Object)

Parameters

Name	Type	Description
criteriaEvaluationBehavior	PersistentCriteriaEvaluationBehavior	A PersistentCriteriaEvaluationBehavior enumeration value that specifies how the persistent criteria is evaluated.
objType	Type	A Type object which represents the type of objects to search for.
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.

Returns

Type	Description
Task<Object>	A Task that returns an object. This object represents the first persistent object that matches the specified criteria. null (Nothing in Visual Basic) if no persistent object is found that matches the criteria.

Remarks

The example below demonstrates how to use this method. Here, session is the Session instance.

C#

using System.Threading;
using DevExpress.Data.Filtering;
using DevExpress.Xpo;
// ...
CancellationTokenSource source = new CancellationTokenSource();
CancellationToken cancellationToken = source.Token;
Person personToUpdate = 
    (Person)await session.FindObjectAsync(PersistentCriteriaEvaluationBehavior.BeforeTransaction, 
    typeof(Person), CriteriaOperator.Parse("Name='Michael Suyama'"), cancellationToken);
if(personToUpdate != null) {
    personToUpdate.Birthday = new DateTime(1986, 10, 31);
    session.Save(personToUpdate);
}

VB.NET

Imports System.Threading
Imports DevExpress.Data.Filtering
Imports DevExpress.Xpo
' ...
Private source As New CancellationTokenSource()
Private cancellationToken As CancellationToken = source.Token
Private personToUpdate As Person = _
    CType(Await session.FindObjectAsync(PersistentCriteriaEvaluationBehavior.BeforeTransaction, _
    GetType(Person), CriteriaOperator.Parse("Name='Michael Suyama'"), cancellationToken), Person)
If personToUpdate IsNot Nothing Then
    personToUpdate.Birthday = New Date(1986, 10, 31)
    session.Save(personToUpdate)
End If

Persistent objects that are marked as deleted in the database (see Deferred and Immediate Object Deletion) are not included in the search.