"COM object that has been separated from its underlying RCW cannot be used" 与 vb.net 表单事件相关的错误

Question

我正在将 arcobjects 地图事件挂接到 vb.net 表单以监听地图选择更改。这一切都很好，但用户在打开表单时偶尔会报告此错误。我看不到任何模式来重现错误，它似乎是随机的。

"COM object that has been separated from its underlying RCW cannot be used"

它源自我挂接事件的 Load() 方法形式。

任何人都可以帮助我了解我做错了什么吗？我正在解除 FormClosing() 事件中的地图选择事件，我认为这是正确的方法。

Public Class MyForm

    Private _activeViewEvents As IActiveViewEvents_Event

    Private Sub FormLoad(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        _activeViewEvents = TryCast(pMxDoc.ActiveView.FocusMap, IActiveViewEvents_Event)
        AddHandler _activeViewEvents.SelectionChanged, AddressOf SelectionChanged    
    End Sub

    Private Sub SelectionChanged
        'do something when selection is changed
    End Sub

    Private Sub FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        RemoveHandler _activeViewEvents.SelectionChanged, AddressOf SelectionChanged
    End Sub

End Class

Answer 1

您用来创建和销毁处理程序的方法是有效的。如果在表单打开时地图文档发生更改，您可能会收到 RCW COM 异常。由于您正在使用 FocusMap 创建句柄，当文档更改时，FocusMap 也会更改，这意味着您需要为新地图文档重新创建句柄。

Answer 2

好的，我想我已经通过使用 ActiveViewChanged 事件解决了这个问题。我没有在每个表单加载或新文档事件上重新挂钩事件，而是尝试监听 ActiveViewChanged 事件何时被触发并每次重新挂钩 SelectionChanged 事件。事实证明，每次打开新文档时都会触发不止一次（不确定为什么）。无论如何，问题似乎已经消失了。下面是一些示例代码：

Public Class MyForm

Private _activeViewEvents As IActiveViewEvents_Event
Private _docEvents As IDocumentEvents_Event

Private Sub FormLoad(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    AddHandler _docEvents.ActiveViewChanged, AddressOf ActiveViewChanged
End Sub

Private Sub ActiveViewChanged()
    Dim maps = pMxDoc.Maps
    For i = 0 to maps.Count - 1 'remove handlers from all maps
        RemoveActiveViewEvents(maps.Item(i))
    Next
    SetupActiveViewEvent(pMxDoc.ActiveView.FocusMap) 'only add handler to active map
End Sub

Private Sub RemoveActiveViewEvents(map As IMap)
    _activeViewEvents = CType(map, IActiveViewEvents_Event)
    RemoveHandler _activeViewEvents.SelectionChanged, AddressOf SelectionChanged
End Sub

Private Sub SetupActiveViewEvents(map As IMap)
    _activeViewEvents = CType(map, IActiveViewEvents_Event)
    AddHandler _activeViewEvents.SelectionChanged, AddressOf SelectionChanged
End Sub

Private Sub SelectionChanged
    'do something when selection is changed
End Sub

End Class

"COM object that has been separated from its underlying RCW cannot be used" 与 vb.net 表单事件相关的错误

"COM object that has been separated from its underlying RCW cannot be used" error related to vb.net form event

vb.net

events

com

arcobjects

rcw