xml - return 语句上的 vba '91' 错误

Question

我编写的以下功能无法正常工作。我在要返回对象的块的最后一行出现臭名昭著的“91”对象变量或 With block variable not set 错误。我不明白为什么，因为我的输入节点确实有具有所需 id 的子节点。MsgBox 告诉我实际上已经找到了节点，因此设置了变量 res。我仍然收到“91”错误。

    Private Function getElementById(root As MSXML2.IXMLDOMNode, id As String) As MSXML2.IXMLDOMNode

    Dim Children As MSXML2.IXMLDOMNodeList
    Dim Child As MSXML2.IXMLDOMNode
    Dim res As MSXML2.IXMLDOMNode
    Dim found As Boolean
    found = False

    If (root.HasChildNodes = True) Then

        Set Children = root.ChildNodes

        For a_counter = 0 To (Children.Length - 1)

            Set Child = Children.Item(a_counter)

            If Child.Attributes.getNamedItem("id").Text = id Then

                Set res = Child
                found = True
                MsgBox "Found"

            End If

        Next a_counter

        If found = False Then
            MsgBox "Not Found"
            res = Nothing
        End If

    Else

        Set res = Nothing
        MsgBox "No Children"

    End If

    getElementById = res

    End Function