为ListBoxItems应用Foreground仅适用于列表框中的Task.Delay [英] Applying Foreground for ListBoxItems only works with Task.Delay in a listbox

问题描述

我正在尝试有选择地将绿色前景应用于列表框中的项目。我使用以下代码来做到这一点：

I am trying to selectively apply a green foreground to items in a listbox. I use the following code to do just that:

  Public Async Sub MarkFromCollection（）

   if lbxLocMins.Items.Count> 0然后'检查列表框是否有项目

    Dim tmpList As New List（Of Integer）'创建临时列表以保存 数据以检查

    tmpList = Await（DataService.CollGetIdMinforL5IDAsync（thisLocality.LocL5ID））'从与MS SQL Server通信的WCF服务获取数据

   如果tmpList.Count> 0然后'检查列表是否包含项目

     Await Task.Delay（50）'避免应用程序崩溃??????? !!!! !!!

     Dim lbi作为ListBoxItem'创建lbi

     For Each b As brkMineral在lbxLocMins.Items'iterate

      if tmpList.Contains（b.IdMin）然后'检查集合中的列表是否匹配 列表框中的项目为
       lbi =新的ListBoxItem'实施lbi

      ;  lbi = CType（lbxLocMins.ContainerFromItem（b），ListBoxItem）'设置lbi

       if Not lbi Is Nothing Then'检查是否lbi什么都没有？
        lbi.Foreground = greenBrush'if if：set foreground to green

     ;   结束如果

     结束如果是
     Next

   结束如果

  结束如果

  End Sub

 Public Async Sub MarkFromCollection()
  If lbxLocMins.Items.Count > 0 Then 'Check if the Listbox has items
   Dim tmpList As New List(Of Integer) 'Create temp list to hold data to check against
   tmpList = Await (DataService.CollGetIdMinforL5IDAsync(thisLocality.LocL5ID)) 'Get Data from a WCF-Service that talks to a MS SQL Server
   If tmpList.Count > 0 Then 'Check if the list contains items
    Await Task.Delay(50) 'avoid App crash???????!!!!!!!
    Dim lbi As ListBoxItem 'Create lbi
    For Each b As brkMineral In lbxLocMins.Items 'iterate
     If tmpList.Contains(b.IdMin) Then 'Check if there is a match between the list from the collection and the items in the listbox
      lbi = New ListBoxItem 'instatiate the lbi
      lbi = CType(lbxLocMins.ContainerFromItem(b), ListBoxItem) 'set the lbi
      If Not lbi Is Nothing Then 'check if lbi is nothing
       lbi.Foreground = greenBrush 'if not: set foreground to green
      End If
     End If
    Next
   End If
  End If
 End Sub

只有包含Task.Delay（50）时代码才能正常工作。如果我对这一行发表评论，该应用程序会在5次中崩溃4次。

The code works as expected only if I have the Task.Delay(50) included. If I comment this line out the app crashes 4 times out of 5.

有人可以帮我理解发生了什么吗？

Can anybody help me understand what is going on?

推荐答案

你得到了什么异常，我猜你得到的是一个没有运行的ui-thread错误？

What exception do you get, I'm guessing you're getting a not-running-on-ui-thread error?

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