XmlReader 循环通过节点

Question

大家好，我有以下代码：

    Using reader As XmlReader = XmlReader.Create(New StringReader(xmlString))
        reader.ReadToFollowing("GridChannel")
        Dim Channel As String = reader.GetAttribute("Channel")
        Dim DisplayName As String = reader.GetAttribute("DisplayName")

        reader.ReadToFollowing("Airings")
        reader.ReadToFollowing("GridAiring")

        Dim Title As String = reader.GetAttribute("Title")
        Dim EpisodeTitle As String = reader.GetAttribute("EpisodeTitle")
        Dim AiringTDurationime As String = reader.GetAttribute("AiringTDurationime")
        Dim isHD As Boolean = Convert.ToBoolean(reader.GetAttribute("isHD"))
        Dim TVRating As String = reader.GetAttribute("TVRating")
    End Using

上面的代码工作得很好，但我在循环 Airings 部分时遇到问题。

该部分的 XML 如下所示：

    <Airings>
        <GridAiring ProgramId="35951" SeriesId="3490" Title="Matlock" EpisodeTitle="Santa Claus" AiringTime="2013-04-12T14:00:00Z" Duration="60" Color="Color" AiringType="Unknown" CC="true" LetterBox="false" Stereo="false" HD="false" SAP="false" TVRating="TV-PG" Dolby="false" DSS="false" HDLevel="HD Level Unknown" DVS="false" Category="Other" Subcategory="drama" Sports="false"/>
        <GridAiring ProgramId="828869" SeriesId="1409" Title="In the Heat of the Night" EpisodeTitle="Hatton's Turn" AiringTime="2013-04-12T15:00:00Z" Duration="60" Color="Color" AiringType="Unknown" CC="true" LetterBox="false" Stereo="false" HD="false" SAP="false" TVRating="TV-PG@V" Dolby="false" DSS="false" HDLevel="HD Level Unknown" DVS="false" Category="Other" Subcategory="crime drama" Sports="false"/>
        <GridAiring ProgramId="978338" SeriesId="1409" Title="In the Heat of the Night" EpisodeTitle="Hatton's Turn" AiringTime="2013-04-12T16:00:00Z" Duration="60" Color="Color" AiringType="Unknown" CC="true" LetterBox="false" Stereo="false" HD="false" SAP="false" TVRating="TV-PG@V" Dolby="false" DSS="false" HDLevel="HD Level Unknown" DVS="false" Category="Other" Subcategory="crime drama" Sports="false"/>
        <GridAiring ProgramId="4210626" Title="WGN Midday News" AiringTime="2013-04-12T17:00:00Z" Duration="60" Color="Color" AiringType="New" CC="true" LetterBox="false" Stereo="true" HD="false" SAP="false" TVRating="None" Dolby="false" DSS="false" HDLevel="HD Level Unknown" DVS="false" Category="News" Subcategory="newscast" Sports="false"/>
        <GridAiring ProgramId="878716" SeriesId="1028666" Title="Walker, Texas Ranger" EpisodeTitle="El Coyote, Part 2" AiringTime="2013-04-12T18:00:00Z" Duration="60" Color="Color" AiringType="Unknown" CC="true" LetterBox="false" Stereo="true" HD="false" SAP="false" TVRating="TV-14@V" Dolby="false" DSS="false" HDLevel="HD Level Unknown" DVS="false" Category="Other" Subcategory="crime drama" Sports="false"/>
    </Airings>

Answer 1

可以循环执行此操作：

While reader.ReadToFollowing("GridAiring")
    Dim Title As String = reader.GetAttribute("Title")
    Dim EpisodeTitle As String = reader.GetAttribute("EpisodeTitle")
    Dim AiringTDurationime As String = reader.GetAttribute("AiringTDurationime")
    Dim isHD As Boolean = Convert.ToBoolean(reader.GetAttribute("isHD"))
    Dim TVRating As String = reader.GetAttribute("TVRating")
End While

Answer 2

不进入XML序列化，为什么不使用XmlReader.GetAttribute？

然后您应该能够将您的代码缩减为：

Dim ServiceId As String = reader.GetAttribute("ServiceId")

等等，这样更易​​读，更容易维护。

编辑： 循环通过 XML，我更喜欢这种方式：

Dim Airings As XDocument = XDocument.Parse(xmlString)
For Each GridAiring As XElement In Airings.Root.Elements
  Dim ProgramId As String = GridAiring.Attribute("ProgramId").Value
  'read other properties here
Next

Answer 3

使用 LINQ 可以获得更好的性能，而不是循环。这是一个将 ProgramId、SeriesId 和 Title 拉入可枚举的示例。

Dim document As XDocument = XDocument.Load("c:\tmp\test.xml")
Dim airings = From i In document.Descendants("Airings")
              Select New With
                     {Key .ProgramId = i.Attribute("ProgramId").Value,
                      Key .SeriesId = i.Attribute("SeriesId").Value,
                      Key .Title = i.Attribute("Title").Value}

然后您可以遍历枚举。一个在控制台中打印结果的小例子

For Each a In airings
    Console.WriteLine(String.Format("{0},{1},{2}", a.ProgramId, a.SeriesId, a.Title))
    Console.Read()
Next

每个项目的想法当然是您可以调用.ProgramId、.SeriesId 等来获取价值

如果您想添加检查以确保 Airing 没有缺少属性并防止可能的异常，您可以在 select 中添加检查以确保它存在，如下所示。

Dim document As XDocument = XDocument.Load("c:\tmp\test.xml")
Dim airings = From i In document.Descendants("Airings")
              Where i.Attribute("ProgramId") IsNot Nothing _
              And i.Attribute("SeriesId") IsNot Nothing _
              And i.Attribute("Title") IsNot Nothing
              Select New With
                     {Key .ProgramId = i.Attribute("ProgramId").Value,
                      Key .SeriesId = i.Attribute("SeriesId").Value,
                      Key .Title = i.Attribute("Title").Value}