Как протестировать или работать с DisconnectedItem в ListView в VS2010?

Question

Я пытаюсь изменить фон ListViewItem из прикрепленного свойства. Следующий код работает до тех пор, пока ListViewItem не будет прокручиваться из отображаемого ListView. Ошибка заключается в том, что таймер запускается в ListViewItem, который был отключен.

{System.Windows.Controls.ListViewItem: {DisconnectedItem}} System.Windows.Controls.ListViewItem

Как проверить для отключенного элемента в Visual Studio 2010?

ТИА

namespace Stargate_V 
{ 
    // Using singleton pattern to create one time to be shared among all ListViewItem instances. 
    public static class ListTimer 
    { 
     // Reasons for using a DispatcherTimer opposed to a System.Timers.Timer are that the DispatcherTimer runs on the same thread as the 
     // Dispatcher and a DispatcherPriority can be set on the DispatcherTimer. Timer runs in its own thread. 
     private static readonly Timer listTimer; 

     static ListTimer() 
     { 
      listTimer = new Timer { AutoReset = true, Enabled = true, Interval = 10 * 1000 }; // Interval in milliseconds 
      listTimer.Elapsed += listTimer_Elapsed; 
     } 

     static void listTimer_Elapsed(object sender, ElapsedEventArgs e) 
     { 
      if (ListTimerEvent != null) 
      { 
       ListTimerEvent(sender, e);  
      } 
     } 

     public static event EventHandler ListTimerEvent; 
    } 

    // Static classes can not implement an interface. (Hence : INotifyPropertyChanged can not be used). 
    public static class ListViewItemBehavior 
    { 

     // Hint: create this with "propa" then tab 

     public static string GetMyValue(DependencyObject obj) 
     { 
      return (string)obj.GetValue(MyValueProperty); 
     } 

     public static void SetMyValue(DependencyObject obj, string value) 
     { 
      obj.SetValue(MyValueProperty, value); 
     } 

     // Using a DependencyProperty as the backing store for MyValue. This enables animation, styling, binding, etc... 
     public static readonly DependencyProperty MyValueProperty = 
      DependencyProperty.RegisterAttached("MyValue", typeof(Object), typeof(ListViewItemBehavior), new UIPropertyMetadata(null, OnMyValueChanged)); 

     static void OnMyValueChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs args) 
     { 
      var item = depObj as ListViewItem; 
      if (item == null) return; 

      // This is unable to pass the instance data: ListTimer.ListTimerEvent +=new EventHandler(ListTimer_ListTimerEvent); 
      // Use an anonymous method in the OnMyValueChanged to specify the timer event handler. This will give access to the specific 
      // ListViewItem. 
      ListTimer.ListTimerEvent += (sender, e) => 
      { 
       Timer timer = sender as Timer; 

       // The Timer is running on a different thread then the ListViewItem item 
       item.Dispatcher.Invoke((Action)(() => 
       { 
--THIS FAILS WHEN ITEM HAS BEEN SCROLLED OUT OF VIEW AND DISCONNECTED --- 
        View_encountertime vt = item.DataContext as View_encountertime; 
        item.Background = Brushes.Azure; 

        // convert checkin time to a datetime. 
        var b = vt.Checkin; 
        DateTime z = (DateTime)vt.Tencounter; 

        // string sdt = DateTime.Now.ToShortDateString() + " " + values[0].ToString(); 
        // DateTime checkin = DateTime.Parse(sdt); 

        // get current time. 
        // DateTime now = DateTime.Now; 
        DateTime now = new DateTime(2015, 2, 13, 11, 30, 5); 
        TimeSpan ts = now.Subtract(z); 

        if (ts.CompareTo(WaitingTime.ninetymin) < 1) item.Background = Brushes.Orange;   // orange 
        if (ts.CompareTo(WaitingTime.seventyfivemin) < 1) item.Background = Brushes.Yellow;  // yellow 
        if (ts.CompareTo(WaitingTime.sixtymin) < 1) item.Background = Brushes.Green;   // green 
        if (ts.CompareTo(WaitingTime.fortyfivemin) < 1) item.Background = Brushes.Turquoise; // turquose 
        if (ts.CompareTo(WaitingTime.thirtymin) < 1) item.Background = Brushes.Blue;   // blue 
        if (ts.CompareTo(WaitingTime.fifteenmin) < 1) item.Background = Brushes.Violet;   // violet 


       })); 


      }; 


     } 
    } 

    // Waiting times 
    public static class WaitingTime 
    { 
     public static TimeSpan fifteenmin; 
     public static TimeSpan thirtymin; 
     public static TimeSpan fortyfivemin; 
     public static TimeSpan sixtymin; 
     public static TimeSpan seventyfivemin; 
     public static TimeSpan ninetymin; 

     static WaitingTime() 
     { 
      fifteenmin = new TimeSpan(0, 15, 0); 
      thirtymin = new TimeSpan(0, 30, 0); 
      fortyfivemin = new TimeSpan(0, 45, 0); 
      sixtymin = new TimeSpan(0, 60, 0); 
      seventyfivemin = new TimeSpan(0, 75, 0); 
      ninetymin = new TimeSpan(0, 90, 0); 
     } 

    } // end class WaitingTime 


} 

Answer 1

не имеет ничего общего с версией Visual Studio. Имеет отношение к версии .NET. В 4.5 и выше вы можете использовать BindingOperations.DisconnectedSource. До 4.5 .NET не показывал этот элемент, поэтому вам нужно выполнить сравнение строк.