我正在从第三方服务器下载一个文件，如下所示：

Try
    req = DirectCast(HttpWebRequest.Create("https://www.example.com/my.xml"), HttpWebRequest)
    req.Timeout = 100000 '100 seconds
    Resp = DirectCast(req.GetResponse(), HttpWebResponse)
    reader = New StreamReader(Resp.GetResponseStream)
    responseString = reader.ReadToEnd()
Catch ex As Exception

End Try

文件my.xml是1.2GB，我收到错误“抛出了'System.OutOfMemoryException'类型的异常”。当我打开Windows任务管理器时，我看到内存使用率仅为总可用内存的70%，IIS工作进程的大小没有增长到使用全部系统内存。当我发现这一点时：https://learn.microsoft.com/en-us/archive/blogs/tom/chat-question-memory-limits-for-32-bit-and-64-bit-processes，因此70%的失败听起来是正确的。
所以现在我考虑将文件分割成更易于管理的小块。但是，我如何做到这一点 * 而不创建单独的文件 *？有没有一种方法，例如每次加载100MB到内存中（考虑到XML节点结尾），或者每次阅读X个XML节点？
当我在谷歌上搜索“从Web服务器读取大型XML文件而不分割成更小的块”时，我只得到了文件分割工具。

更新1

根据Lex Li的建议，我搜索并找到了这个教程：https://learn.microsoft.com/en-us/dotnet/standard/linq/perform-streaming-transform-large-xml-documents
所以我翻译了代码，它的工作原理和教程一样：

Private Shared Iterator Function StreamCustomerItem(ByVal uri As String) As IEnumerable(Of XElement)
    Using reader As XmlReader = XmlReader.Create(uri)
        Dim name As XElement = Nothing
        Dim item As XElement = Nothing
        reader.MoveToContent()

        While reader.Read()

            If reader.NodeType = XmlNodeType.Element AndAlso reader.Name = "Customer" Then

                While reader.Read()

                    If reader.NodeType = XmlNodeType.Element AndAlso reader.Name = "Name" Then
                        name = TryCast(XElement.ReadFrom(reader), XElement)
                        Exit While
                    End If
                End While

                While reader.Read()
                    If reader.NodeType = XmlNodeType.EndElement Then Exit While

                    If reader.NodeType = XmlNodeType.Element AndAlso reader.Name = "Item" Then
                        item = TryCast(XElement.ReadFrom(reader), XElement)

                        If item IsNot Nothing Then
                            Dim tempRoot As XElement = New XElement("Root", New XElement(name))
                            tempRoot.Add(item)
                            Yield item
                        End If
                    End If
                End While
            End If
        End While
    End Using
End Function

Private Shared Sub Main()
    Dim srcTree As IEnumerable(Of XElement) = From el In StreamCustomerItem("https://www.example.com/source.xml") Select New XElement("Item", New XElement("Customer", CStr(el.Parent.Element("Name"))), New XElement(el.Element("Key")))
    Dim xws As XmlWriterSettings = New XmlWriterSettings()
    xws.OmitXmlDeclaration = True
    xws.Indent = True

    Using xw As XmlWriter = XmlWriter.Create(HttpContext.Current.Server.MapPath("files\") + "Output.xml", xws)
        xw.WriteStartElement("Root")

        For Each el As XElement In srcTree
            el.WriteTo(xw)
        Next

        xw.WriteEndElement()
    End Using

End Sub

上面的示例转换了output.xml中的source.xml，但我只想完全按原样读取product节点（不需要转换），并以这样的方式读取单个节点，以便我可以处理大型XML文件。
我试着重写它，这样它就可以从我的XML中提取值，就像下面的结构一样。首先，我试着从我的xml文件中准备一些东西，如下所示：

Private Shared Iterator Function StreamCustomerItem(ByVal uri As String) As IEnumerable(Of XElement)
    Using reader As XmlReader = XmlReader.Create(uri)
        Dim name As XElement = Nothing
        Dim item As XElement = Nothing
        reader.MoveToContent()

        While reader.Read()
            If reader.NodeType = XmlNodeType.Element AndAlso reader.Name = "Id" Then
                name = TryCast(XElement.ReadFrom(reader), XElement)
                item = TryCast(XElement.ReadFrom(reader), XElement)

                If item IsNot Nothing Then
                    Dim tempRoot As XElement = New XElement("Root", New XElement(name))
                    tempRoot.Add(item)
                    Yield item
                End If

                Exit While
            End If
        End While
    End Using
End Function

Private Shared Sub Main()
    Dim srcTree As IEnumerable(Of XElement)

    srcTree = From el In StreamCustomerItem("https://www.example.com/mysource.xml")
              Select New XElement("product", New XElement("product", CStr(el.Parent.Element("Id"))))

    Dim xws As XmlWriterSettings = New XmlWriterSettings()
    xws.OmitXmlDeclaration = True
    xws.Indent = True

    Using xw As XmlWriter = XmlWriter.Create(HttpContext.Current.Server.MapPath("files\") + "Output.xml", xws)
        xw.WriteStartElement("Root")

        For Each el As XElement In srcTree
            el.WriteTo(xw)
        Next

        xw.WriteEndElement()
    End Using

End Sub

这只是将<Root />写入到我的output.xml中
mysource.xml

<?xml version="1.0" encoding="UTF-8" ?>
<products>
    <product>
        <Id>
            <![CDATA[122854]]>
        </Id>
        <Type>
            <![CDATA[restaurant]]>
        </Type>
        <features>
            <wifi>
                <![CDATA[included]]>
            </wifi>
        </features>         
    </product>
</products>

所以总结一下我的问题：如何从“mysource.xml”中按原样读取单个product节点，而不将整个文件加载到内存中？

更新1

Private Shared Iterator Function StreamCustomerItem(ByVal uri As String) As IEnumerable(Of XElement)
    Using reader As XmlReader = XmlReader.Create(uri)
        Dim name As XElement = Nothing
        Dim item As XElement = Nothing
        reader.MoveToContent()

        While Not reader.EOF
            If reader.NodeType = XmlNodeType.Element AndAlso reader.Name = "product" Then
                Dim el As XElement = TryCast(XElement.ReadFrom(reader), XElement)
                If el IsNot Nothing Then Yield el
            Else
                reader.Read()
            End If
        End While
    End Using
End Function            

Private Shared Sub Main()
    Dim element As IEnumerable(Of XmlElement) = From el In StreamCustomerItem("source.xml") Select el

    For Each str As XmlElement In grandChildData
    'here loop through `product` element
        Console.WriteLine(str)
    Next
End Sub

我的完整测试文件通过洋葱分享（使用TOR浏览器下载）：
http://jkntfybog2s5cc754sn7mujvyaawdqxd4q5imss66x3hsos34rrbjrid.onion密钥：黄色建筑物