Dispatcher.BeginInvoke在一种情况下没有被执行

时间：2014-08-08 09:18:47

标签： c# .net multithreading dispatcher

我正在尝试修复现有应用程序中的错误，在单一情况下，调度事件未被执行。

在我们的应用程序中，有几个服务实现了一个公共抽象类（AbstractService）。当服务保存实体并且必须在UI线程中发出通知时，我遇到了这个问题。

AbstractService的相关部分：

public abstract class AbstractService<TEntity, TData, TInfo> : IDataProvider, IAbstractService
    where TEntity : AbstractEntity, new()
    where TData : AbstractData<TEntity>
    where TInfo : IEntityInfo {

    [...]

    protected virtual void NotifyEntityChanged(NotifyEventItem<TInfo>[] pNotifyEventItems) { }

    private void NotifyPersPlanChanged() {
        if (PersPlanChanged != null)
            PersPlanChanged(this, new NotifyEventArgs<IEntityInfo>(null, PersistanceState.Reset));

        Debug.WriteLine(string.Format("{0} {1} Call {2} to NotifyPersPlanChanged",
            DateTime.Now.ToLongTimeString(), GetType().Name, m_counterNotifyPersPlanChanged++));
    }

    private static int m_counterInternalFireNotification;
    private void InternalFireNotification(List<NotifyEventItem<TInfo>> pNotifyEventItem) {
        if (pNotifyEventItem == null || pNotifyEventItem.Count == 0)
            return;

        Debug.WriteLine(string.Format("{0} {1} Call {2} to InternalFireNotification",
            DateTime.Now.ToLongTimeString(), GetType().Name, m_counterInternalFireNotification++));

        // do not call the event handlers directly, because a transaction may be in progress and
        // we want the event handlers to see the end results of the modifications.
        Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, new HandleEntityChanged(NotifyEntityChanged), pNotifyEventItem.ToArray());
        Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, new HandlePersPlanChanged(NotifyPersPlanChanged));
    }
}

每次通过服务修改实体的属性时，都会调用NotifyEntityChanged。

以下是~20中AbstractService的两个实现。第一个是我遇到问题的，第二个是作品。我将进一步描述问题所在。

public class ErgaenzungsfeldService : AbstractServiceBasic<ErgaenzungsfeldEntity, ErgaenzungsfeldData>, IErgaenzungsfeldService {

    [...]

    [EventPublication(Constants.TopicErgaenzungsfeldChanged, PublicationScope.Global)]
    public event EventHandler ErgaenzungsfeldChanged;

    private static int m_counterNotifyEntityChanged;
    protected override void NotifyEntityChanged(NotifyEventItem<IEntityInfoBasic>[] pNotifyEventItems) {
        Debug.WriteLine(string.Format("{0} {1} Call {2} to NotifyEntityChanged",
            DateTime.Now.ToLongTimeString(), GetType().Name, m_counterNotifyEntityChanged++));

        base.NotifyEntityChanged(pNotifyEventItems);
        if (ErgaenzungsfeldChanged != null) {
            ErgaenzungsfeldChanged(this, new NotifyEventArgs<IEntityInfoBasic>(pNotifyEventItems));
        }
    }
}

public class DienstleistenderService : AbstractAdaLanguageDependentServiceVersion<DienstleistenderEntity, DienstleistenderData>, IDienstleistenderService {

    [...]

    [EventPublication(Constants.TopicDienstleistenderChanged, PublicationScope.Global)]
    public event EventHandler DienstleistenderChanged;

    private static int m_counterNotifyEntityChanged;
    protected override void NotifyEntityChanged(NotifyEventItem<IEntityInfoVersion>[] pNotifyEventItem) {
        Debug.WriteLine(string.Format("{0} {1} Call {2} to NotifyEntityChanged",
            DateTime.Now.ToLongTimeString(), GetType().Name, m_counterNotifyEntityChanged++));
        if (DienstleistenderChanged != null) {
            DienstleistenderChanged(this, new NotifyEventArgs<IEntityInfoVersion>(pNotifyEventItem));
        }
    } 
 }

所有服务都实例化如下：

WorkItem.RootWorkItem.Services.AddNew<ErgaenzungsfeldService, IErgaenzungsfeldService>();
WorkItem.RootWorkItem.Services.AddNew<DienstleistenderService, IDienstleistenderService>();

使用以下两种方式之一进行访问：

WorkItem.Services.Get<IDienstleistenderService>()

[ServiceDependency]
public IErgaenzungsfeldService ErgaenzungsfeldService { get; set; }

问题：并非总是会调用ErgaenzungsfeldService.NotifyEntityChanged。这仅在导入数据时发生，而不是在“正常”使用应用程序时发生。通常我的意思是可以在应用程序中修改ErgaenzungsfeldEntity并保存。正在使用相同的机制并且有效。

一些观察结果：

  • 导入过程是单线程的。它不在UI线程中运行。
  • 正确调用DienstleistenderService.NotifyEntityChanged，当ErgaenzungsfeldService.NotifyEntityChanged不是
    • 时
  • 正确地将Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, new HandleEntityChanged(NotifyEntityChanged), pNotifyEventItem.ToArray())替换为NotifyEntityChanged(pNotifyEventItem.ToArray())或System.Windows.Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, new HandlePersPlanChanged(NotifyPersPlanChanged));来调用ErgaenzungsfeldService.NotifyEntityChanged。当UI从另一个线程获得通知时，应用程序显然会在以后抛出异常。
  • 如果通过用户界面保存了ErgaenzungsfeldEntity，则正确调用ErgaenzungsfeldService.NotifyEntityChanged。

以下是为调试目的而添加的消息输出，以帮助我分析问题。

09:39:44 ErgaenzungsfeldService Call 0 to InternalFireNotification
09:39:44 ErgaenzungsfeldService Call 1 to InternalFireNotification
09:39:44 ErgaenzungsfeldService Call 2 to InternalFireNotification
09:39:44 ErgaenzungsfeldService Call 3 to InternalFireNotification
09:40:08 DienstleistenderService Call 0 to InternalFireNotification
09:40:08 DienstleistenderService Call 1 to InternalFireNotification
09:40:09 DienstleistenderService Call 2 to InternalFireNotification
[...]
09:40:14 DienstleistenderService Call 652 to InternalFireNotification
09:40:14 DienstleistenderService Call 653 to InternalFireNotification
09:40:14 DienstleistenderService Call 654 to InternalFireNotification
09:40:14 DienstleistenderService Call 655 to InternalFireNotification
09:40:14 AdaService Call 0 to InternalFireNotification
09:40:14 DienstleistenderService Call 656 to InternalFireNotification
09:40:14 DienstleistungService Call 0 to InternalFireNotification
09:40:14 AufbauorganisationService Call 0 to InternalFireNotification
09:40:14 AufbauorganisationService Call 1 to InternalFireNotification
09:40:14 AdaService Call 0 to NotifyPersPlanChanged
09:40:14 DienstleistenderService Call 0 to NotifyEntityChanged
09:40:16 DienstleistenderService Call 0 to NotifyPersPlanChanged
09:40:16 DienstleistungService Call 0 to NotifyPersPlanChanged
09:40:16 AufbauorganisationService Call 0 to NotifyPersPlanChanged
09:40:16 AufbauorganisationService Call 1 to NotifyPersPlanChanged

问题：什么可能导致通知不按照描述执行？

[编辑] 我通过存储DispatcherOperation来获得更多洞察力：

private List<DispatcherOperation> m_dispatcherOperationresults = new List<DispatcherOperation>();
private void InternalFireNotification(List<NotifyEventItem<TInfo>> pNotifyEventItem) {
   if (pNotifyEventItem == null || pNotifyEventItem.Count == 0)
      return;

   m_log.DebugFormat("InternalFireNotification called for {0}. TInfo type is {1}", GetType(), typeof(TInfo));

   // do not call the event handlers directly, because a transaction may be in progress and
   // we want the event handlers to see the end results of the modifications.
   DispatcherOperation result = Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Send, new HandleEntityChanged(NotifyEntityChanged), pNotifyEventItem.ToArray());
   m_dispatcherOperationresults.Add(result);
   Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.ApplicationIdle, new HandlePersPlanChanged(NotifyPersPlanChanged));
}

这表明委托执行卡在执行队列中。无论DispatcherPriority设置为ApplicationIdle（一如既往）还是Send（优先级最高），它们都会因ErgaenzungsfeldService而停滞不前。

在此打印屏幕中，项目0-3已在导入期间从非UI线程触发并保持挂起状态，而项目4已从GUI线程触发（几分钟后）并执行 dispatcher priority results

问题：这些代表在某些课程中仍然处于等待状态的原因可能是什么原因？

1 个答案:

答案 0 :(得分：1)

只是为了让我的评论“正式”。这可能是由另一个线程调用Dispatcher.CurrentDispatcher引起的。这可能导致应用程序创建一个没有任何UI访问权限的新调度程序。

假设您正在从UI创建ErgaenzungsfeldService类，则可以创建一个值为Dispatcher.CurrentDispatcher的只读Dispatcher字段。这将为您提供UI调度程序。

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