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Session.FindObjectAsync<ClassType>(PersistentCriteriaEvaluationBehavior, CriteriaOperator, CancellationToken) Method

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

Namespace: DevExpress.Xpo

Assembly: DevExpress.Xpo.v19.2.dll

Declaration

public Task<ClassType> FindObjectAsync<ClassType>(
    PersistentCriteriaEvaluationBehavior criteriaEvaluationBehavior,
    CriteriaOperator criteria,
    CancellationToken cancellationToken = default(CancellationToken)
)
Public Function FindObjectAsync(Of ClassType)(
    criteriaEvaluationBehavior As PersistentCriteriaEvaluationBehavior,
    criteria As CriteriaOperator,
    cancellationToken As CancellationToken = Nothing
) As Task(Of ClassType)
public Task<ClassType> FindObjectAsync<ClassType>(
    PersistentCriteriaEvaluationBehavior criteriaEvaluationBehavior,
    CriteriaOperator criteria,
    CancellationToken cancellationToken = default(CancellationToken)
)
Public Function FindObjectAsync(Of ClassType)(
    criteriaEvaluationBehavior As PersistentCriteriaEvaluationBehavior,
    criteria As CriteriaOperator,
    cancellationToken As CancellationToken = Nothing
) As Task(Of ClassType)

Parameters

Name Type Description
criteriaEvaluationBehavior PersistentCriteriaEvaluationBehavior

A PersistentCriteriaEvaluationBehavior enumeration value that specifies how the persistent criteria is evaluated.

criteria CriteriaOperator

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

cancellationToken CancellationToken

A CancellationToken object that delivers a cancellation notice to the running operation.

Parameters

Name Type Description
criteriaEvaluationBehavior PersistentCriteriaEvaluationBehavior

A PersistentCriteriaEvaluationBehavior enumeration value that specifies how the persistent criteria is evaluated.

criteria CriteriaOperator

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

cancellationToken CancellationToken

A CancellationToken object that delivers a cancellation notice to the running operation.

Returns

Type Description
Task<ClassType>

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.

Returns

Type Description
Task<ClassType>

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.

Type Parameters

Name Description
ClassType

Type Parameters

Name Description
ClassType

Remarks

Below is an example of using the FindObjectAsync<ClassType> method. Here, session is the Session instance.

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

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

See Also