为什么这个 NServiceBus 消息处理程序在调用 Task.CompletedTask 时抛出 System.MethodAccessException？

Question

在查看文档并试图找到开发人员遇到此错误的其他示例后，我有点卡住了。我们正在使用 NServiceBus 6，偶尔会在调用 return Task.CompletedTask 的消息处理程序中得到 System.MethodAccessException。它似乎只在处理程序部署在 Azure 辅助角色中时发生（与模拟器中的运行相反）。我们正在使用 Azure 服务总线传输。

  public Task Handle(UpdatePatientAccommodationCode message, IMessageHandlerContext context)
    {
        Console.WriteLine($"Handling [{message.GetType()}]");
        var patientVisit = LoadByExternalPatientId(message.ClientId, message.ExternalPatientId);

        var mappedEvent = patientVisit.HandleCommand(message);

        if (patientVisit.IsEventAdded)
            PatientVisitEventStore.Save(patientVisit);

        return mappedEvent == null ? Task.CompletedTask : context.Publish(mappedEvent);
    }

实际异常是这样的：

System.MethodAccessException: Attempt by method 'XXX.Handlers.PatientVisitHandler.Handle(XXX.UpdatePatientAccommodationCode, NServiceBus.IMessageHandlerContext)' to access method 'System.Threading.Tasks.Task.get_CompletedTask()' failed.
at XXX.Handlers.PatientVisitHandler.Handle(UpdatePatientAccomm     odationCode message, IMessageHandlerContext context) in PatientVisitHandler.cs:  line 314
at NServiceBus.InvokeHandlerTerminator.Terminate(IInvokeHandlerContext context)       in   C:\BuildAgent\work06e2123f54fce4\src\NServiceBus.Core\Pipeline\Incoming\Invok  eHandlerTerminator.cs: line 24
at NServiceBus.LoadHandlersConnector.<Invoke>d__1.MoveNext() in     C:\BuildAgent\work06e2123f54fce4\src\NServiceBus.Core\Pipeline\Incoming\LoadH   andlersConnector.cs: line 40

Answer 1

我怀疑你的本地代码有 .NET framework 4.6.x 支持 Task.CompletedTask。当您部署到 CS 并使用 OS family less than version 5 won't have support for 4.6.x You either will need to use a startup task to install 4.6.x or migrate to OS Family 5 (Server 2016).

Answer 2

这很奇怪。从 Task.CompletedTask I can't come up with a scenario where this could happen. The task that is statically cached is initialized with RAN_TO_COMPLETION 和 DO_NOT_DISPOSE 的参考来源判断。基于此，我建议您确定您使用的是 .NET Framework 4.6 版还是更高版本。如果您这样做并且仍然看到异常，请尝试将 Task.CompletedTask 替换为

static class TaskEx
{
   public static readonly Task CompletedTask = Task.FromResult(0); 
}

为什么这个 NServiceBus 消息处理程序在调用 Task.CompletedTask 时抛出 System.MethodAccessException？

Why does this NServiceBus message handler throw System.MethodAccessException on call to Task.CompletedTask?

nservicebus

azure