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我有一个看起来像的 XML 文件

<?xml version="1.0">
<playlist>
     <name>My Playlist</name>
     <song>
         <name>Song Name Here</name>
         <path>Path to song here</path>
         <note>Song notes here</note>
         <artist>Song artist here</artist>
         <type>Song type here</type>
     </song>
     <song>
         <name>Song Name Here</name>
         <path>Path to song here</path>
         <note>Song notes here</note>
         <artist>Song artist here</artist>
         <type>Song type here</type>
     </song>
</playlist>

我正在尝试从 xml 文件中删除歌曲节点，但我无法找出错误的原因。我还在学习视觉基础知识。

错误：对象引用未设置为对象的实例。

这是我的代码

    Private Sub MsItemRemoveClick(sender As System.Object, e As EventArgs) Handles msItemRemove.Click

        If lvwPlaylist.SelectedItems.Count > 0 Then

            Dim xmlDoc As New XmlDocument

            xmlDoc.Load(_playlistpath & lblPlaylistName.Text & ".xml")

            Dim songs As XmlElement = xmlDoc.SelectSingleNode("song")

            For Each item As ListViewItem In lvwPlaylist.SelectedItems

                For Each node As XmlElement In songs

                    If node.SelectSingleNode("name").InnerText = item.SubItems(0).Text Then

                        MsgBox(node.SelectSingleNode("name").InnerText) '<------ this is where the error pops up on 'node.ParentNode.RemoveAll()

                    End If

                Next

                item.Remove()

            Next

            xmlDoc.Save(_playlistpath & lblPlaylistName.Text & ".xml")

        End If

    End Sub

我的努力是遍历所有选定的列表视图项目，如果歌曲名称与歌曲名称匹配，songs node则删除name

4

1 回答 1

1

为了清楚起见，去掉了 ListView....

对于这个 XML 文件...

<?xml version="1.0"?>
<playlist>
     <name>My Playlist</name>
     <song>
         <name>Alpha song</name>
         <path>Path to song here</path>
         <note>Song notes here</note>
         <artist>Song artist here</artist>
         <type>Song type here</type>
     </song>
     <song>
         <name>Beta song</name>
         <path>Path to song here</path>
         <note>Song notes here</note>
         <artist>Song artist here</artist>
         <type>Song type here</type>
     </song>
     <song>
         <name>Charlie song</name>
         <path>Path to song here</path>
         <note>Song notes here</note>
         <artist>Song artist here</artist>
         <type>Song type here</type>
     </song>
     <song>
         <name>Delta song</name>
         <path>Path to song here</path>
         <note>Song notes here</note>
         <artist>Song artist here</artist>
         <type>Song type here</type>
     </song>
</playlist>

在磁盘上保存为 C:\Junk\Junk1.xml，此代码将找到并删除两个中间节点...

Private Sub Button3_Click(sender As System.Object, e As System.EventArgs) Handles Button3.Click
  Dim strFilenameIn As String = "C:\Junk\Junk1.xml"
  Dim strFilenameOut As String = "C:\Junk\Junk2.xml"

  Dim lstNames As New List(Of String)
  lstNames.Add("Beta song")
  lstNames.Add("Charlie song")

  Dim xmlDoc As New XmlDocument
  xmlDoc.Load(strFilenameIn)
  For Each strSongName As String In lstNames
    Dim xnl As XmlNodeList = xmlDoc.SelectNodes("/playlist/song/name")
    For i As Integer = xnl.Count - 1 To 0 Step -1
      Dim xnd As XmlNode = xnl(i)
      If xnd.FirstChild.Value = strSongName Then 'match'
        xmlDoc.DocumentElement.RemoveChild(xnd.ParentNode)
      End If
    Next
  Next strSongName
  xmlDoc.Save(strFilenameOut)
  MsgBox("Finished")
End Sub
于 2012-06-14T01:01:47.280 回答