InvalidOperationException: 集合已修改; 列舉作業可能尚未執行。
StackTrace:
   於 System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   於 System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   於 System.Linq.Enumerable.<SkipIterator>d__31`1.MoveNext()
   於 System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   於 System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   於 System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   於 BetterClip.Service.Windows.ActiveWindowService.<.ctor>b__6_3(EventPattern`1 _)
   於 System.Reactive.AnonymousSafeObserver`1.OnNext(T value)
   於 System.Reactive.Linq.ObservableImpl.Where`1.Predicate._.OnNext(TSource value)
   於 System.Reactive.Linq.ObservableImpl.Throttle`1._.Propagate(UInt64 currentid)
   於 System.Reactive.Concurrency.Scheduler.Invoke[TState](ValueTuple`2 tuple)
   於 System.Reactive.Concurrency.Scheduler.<>c__78`1.<ScheduleAction>b__78_0(IScheduler _, ValueTuple`2 tuple)
   於 System.Reactive.Concurrency.UserWorkItem`1.Run()
   於 System.Reactive.Concurrency.ConcurrencyAbstractionLayerImpl.Timer.Tick()
   於 System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   於 System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   於 System.Threading.TimerQueueTimer.CallCallback()
   於 System.Threading.TimerQueueTimer.Fire()
   於 System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   於 System.Threading.ThreadPoolWorkQueue.Dispatch()