为什么我不能从集合中获取项目并将其存储在变量中？

我有一个收藏，我曾经有一张String -> MailItem地图。我填写了地图，当我找到重复的钥匙时，我想阅读收藏中的物品。

这似乎很简单，但是我花了一个多小时试图弄清楚为什么我不能将Collection项分配给局部变量。（请参见PROBLEM下面的代码）

oMailOther = cMails.Item(cMailKey) “未设置对象变量或带块变量”

Set oMailOther = cMails.Item(cMailKey) “所需对象”

另cMails(cMailKey)一种形式给出相同的错误。调动暗淡没有任何区别。cMails必须可用，因为它在方法的早期使用。请注意Debug.Print此语句之前的那行有效。我想念什么？

Option Explicit
Option Compare Text
 
Public cMails As Collection
 
Public Sub GetOutlookAttachments()
    Set cMails = New Collection

    Dim oStore As Store
    For Each oStore In Session.Stores
        If oStore.DisplayName = "Outlook Data File" Then
            ProcessFolder oStore.GetRootFolder()
        End If
    Next
End Sub
 
Private Sub ProcessFolder(oFolder As Folder)
    Debug.Print oFolder.FolderPath
    ProcessItems oFolder.Items

    Dim oSubFolder As Folder
    For Each oSubFolder In oFolder.Folders
        ProcessFolder oSubFolder ' recurse
    Next
End Sub
 
Private Sub ProcessItems(oItems As Items)
    Dim oItem As Object
    For Each oItem In oItems
        DoEvents
        If TypeOf oItem Is MailItem Then
            Dim oMail As MailItem
            Set oMail = oItem
            Dim cMailKey As String
            cMailKey = oMail.ConversationID & "-" & oMail.ConversationIndex
            If Not Contains(cMails, cMailKey) Then
                cMails.Add oMail.Subject, cMailKey
            Else
                Debug.Print cMails.Item(cMailKey)
                Dim oMailOther As MailItem
 PROBLEM        oMailOther = cMails.Item(cMailKey)
                Debug.Print cMailKey & ": " & oMailOther.Subject
            End If
        ElseIf TypeOf oItem Is MeetingItem Then
            ' ignore
        Else
            Debug.Print "oItem Is a " & TypeName(oItem)
        End If
    Next oItem
End Sub

Public Function Contains(col As Collection, key As Variant) As Boolean
    Dim obj As Variant
    On Error GoTo err
    Contains = True
    obj = col(key)
    Exit Function
err:
    Contains = False
End Function

我还尝试在其他地方复制类似内容Add并进行Item调用，并且可以正常工作。

Public Sub Test()
    Set cMails = New Collection
    
    Dim cMailKey As String
    cMailKey = "hello"
    cMails.Add Session.Stores.Item(1), cMailKey
    
    Debug.Print cMails(cMailKey)
    Dim oStore As Store
    Set oStore = cMails(cMailKey)
    Debug.Print oStore.DisplayName
End Sub