将SynchronizationContext与TrackingParticipant一起使用

Question

我有一个自定义的跟踪参与者：

public class ErsTrackingParticipant : TrackingParticipant, IErsTrackingParticipant
{
    private readonly INHibernateRepository<ErsTrackingRecord> _ersTrackingRecordRepository;
    public ErsTrackingParticipant(INHibernateRepository<ErsTrackingRecord> ersTrackingRecordRepository)
    {
        this._ersTrackingRecordRepository = ersTrackingRecordRepository;
    }
    protected override void Track(TrackingRecord record, TimeSpan timeout)
    {
        ErsTrackingRecord ersTrackingRecord = TrackingCommand.GetTrackingRecord(record);
        this._ersTrackingRecordRepository.Save(ersTrackingRecord);
    }
}
public interface IErsTrackingParticipant
{
}

和一个工作流主机助手：

public class WorkflowHostHelper: IWorkflowHostHelper
{
    private WorkflowApplication _workflowApplication;
    AutoResetEvent _instanceUnloaded = new AutoResetEvent(false);
    private IErsTrackingParticipant _ersTrackingParticipant;
    private bool _isCompleted = false;
    public string InstanceStoreConnectionString { get { return ConfigurationManager.AppSettings["InstanceStoreConnectionString"]; } }
    public WorkflowHostHelper(IErsTrackingParticipant ersTrackingParticipant)
    {
        _ersTrackingParticipant = ersTrackingParticipant;
    }
    public void Initialize(Activity workflowType)
    {
        _workflowApplication = new WorkflowApplication(workflowType);
        TrackingProfile trackingProfile = new TrackingProfile() { Name = "TroubleshootingProfile", ActivityDefinitionId = "*" };
        trackingProfile.Queries.Add(new WorkflowInstanceQuery { States = { "*" } });
        trackingProfile.Queries.Add(new ActivityStateQuery { States = { "*" } });
        trackingProfile.Queries.Add(new ActivityScheduledQuery());
        trackingProfile.Queries.Add(new BookmarkResumptionQuery() { Name = "*" });
        _workflowApplication.Extensions.Add(_ersTrackingParticipant);
        SynchronizationContext synchronizationContext = SynchronizationContext.Current;
        _workflowApplication.SynchronizationContext = synchronizationContext;
        _workflowApplication.InstanceStore = new SqlWorkflowInstanceStore(InstanceStoreConnectionString);
        _workflowApplication.PersistableIdle = (e) =>
            { return PersistableIdleAction.Persist; };
        _workflowApplication.Completed = (e) =>
            {
                _isCompleted = true;
                _instanceUnloaded.Set();
            };
        _workflowApplication.Idle = (e) =>
            { _instanceUnloaded.Set(); };
    } //Rest ommiitted...

当存储库试图保存回数据库时，它会出错：

'((SharpArch.NHibernate.NHibernateRepositoryWithTypedId<EmployeeRequestSystem.Domain.ErsTrackingRecord,int>)(this._ersTrackingRecordRepository)).Session' threw an exception of type 'System.NullReferenceException'
SharpArch.NHibernate.Contracts.Repositories.INHibernateRepositoryWithTypedId<T,TId>.DbContext = {SharpArch.NHibernate.DbContext}

在工作流活动中，我可以参考上下文并使用服务定位器，例如：

    protected override void CacheMetadata(CodeActivityMetadata metadata)
    {
        base.CacheMetadata(metadata);
        metadata.AddDefaultExtensionProvider<INHibernateRepository<AuthorisationRequest>>(
            () => new NHibernateRepository<AuthorisationRequest>());
    }

    protected override void Execute(CodeActivityContext context)
    {
        var authorisationRequestRepoistory = context.GetExtension<INHibernateRepository<AuthorisationRequest>>();

如何将正确的上下文传递给我的ErsTrackingParticipant？

Answer 1

根据您的问题，我不清楚SynchronizationContext与null引用有什么关系。如果你能准确地找到什么是空的，那会很有帮助。

SynchronizationContext.Current属性在大多数情况下都为null。只有当由托管环境中的某个东西设置时，它才会有值。除非发现SynchronizationContext.Current有值，否则我不会设置WorkflowApplication.Synchronization上下文属性。

我不明白你为什么想要跟踪参与者的"上下文"。你指的是什么"语境"？SynchronizationContext？CodeActivityContext？