BackgroundWorker或（Dispatcher）操作在完成ReportProgress时已经完成

Question

我使用DispatcherTimer，因为我需要每隔几分钟执行一次操作。在这个内部我打电话BackgroundWorker来完成我的工作，然后使用定时器上的调度器来更新我的UI。我在想我得到的错误与计时器有关，但我不确定。调度员完成了还是后台工作？我该如何做foreach中的ReportProgress？

错误：

This operation has already had OperationCompleted called on it and further calls are illegal.

执行此操作时：

(sender as BackgroundWorker).ReportProgress((counterTotalSteps/100) * counterOnStep); 

这里是简化：

DispatcherTimer dispTimer = new DispatcherTimer(); 
Dispatcher dispatcher = dispTimer.Dispatcher; 
dispTimer.Tick += delegate {dispTimer_Tick(dispatcher); }; 
dispTimer.Interval = new TimeSpan(0, 0, 45); 
dispTimer.Start(); 

private void DoWork(object sender,Dispatcher dispatcher) 
{ 
    int counterTotalSteps = PartialEmployees.Count(); 
    int counterOnStep = 1; 

    dispatcher.BeginInvoke(new Action(() => 
    {     
     AllEmployees.Clear(); 
     //calling the ReportProgress here works 
     foreach (var item in PartialEmployees) 
     { 
      counterOnStep ++; 
      //part below throws the error 
      (sender as BackgroundWorker).ReportProgress((counterTotalSteps/100) *  counterOnStep); 
      AllEmployees.Add(item);      
     } 
     counterOnStep = 0;    
    }));   
} 

编辑： 堆栈跟踪：

事件

at System.ComponentModel.AsyncOperation.VerifyNotCompleted() 
    at System.ComponentModel.AsyncOperation.Post(SendOrPostCallback d, Object arg) 
    at System.ComponentModel.BackgroundWorker.ReportProgress(Int32 percentProgress, Object userState) 
    at System.ComponentModel.BackgroundWorker.ReportProgress(Int32 percentProgress) 
    at testDispatcher.ViewModel.EmployeeListViewModel.<>c__DisplayClass7.<DoWork>b__6() in C:\Users\kozaj\Documents\Visual Studio 2010\Projects\testDispatcher\testDispatcher\ViewModel\EmployeeListViewModel.cs:line 91 
    at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) 
    at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) 
    at System.Windows.Threading.DispatcherOperation.InvokeImpl() 
    at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) 
    at System.Threading.ExecutionContext.runTryCode(Object userData) 
    at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) 
    at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) 
    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) 
    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) 
    at System.Windows.Threading.DispatcherOperation.Invoke() 
    at System.Windows.Threading.Dispatcher.ProcessQueue() 
    at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) 
    at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) 
    at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) 
    at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) 
    at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) 
    at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) 
    at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) 
    at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) 
    at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) 
    at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) 
    at System.Windows.Threading.Dispatcher.Run() 
    at System.Windows.Application.RunDispatcher(Object ignore) 
    at System.Windows.Application.RunInternal(Window window) 
    at System.Windows.Application.Run(Window window) 
    at System.Windows.Application.Run() 
    at testDispatcher.App.Main() in C:\Users\kozaj\Documents\Visual Studio 2010\Projects\testDispatcher\testDispatcher\obj\x86\Debug\App.g.cs:line 50 
    at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) 
    at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) 
    at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() 
    at System.Threading.ThreadHelper.ThreadStart_Context(Object state) 
    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) 
    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) 
    at System.Threading.ThreadHelper.ThreadStart() 

Answer 1

序列

1. DoWork的被称为
2. DoWork的把 “AllEmployees.Clear（）;”进入调度员队列
3. DoWork完成
4. 调度员看到“AllEmployees.Clear（）;”并开始处理该功能。

我建议仅在实际具有UI交互的步骤中使用dispatcher.Invoke（它立即运行它）。

Answer 2

由于您的工作是在UI线程上完成的，因此根本不应该使用BackgroundWorker。

相反，您应该直接在循环内更新进度条。