c# - 在 VB 中读取 XML

Question

我想在我的应用程序中读取 iTunes 音乐库 XML，但是我不知道如何执行此操作，我想做的是搜索特定轨道名称和规范键，例如“艺术家"、"Album"等。是的，我知道如何使用 iTunes COM，但有些轨道信息无法通过它访问，例如如果轨道是“Explicit”，则有一个附加键

<key>Explicit</key><true/>

我想做的是搜索特定轨道名称并检查它是否有明确的键。

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Major Version</key><integer>1</integer>
    <key>Minor Version</key><integer>1</integer>
    <key>Date</key><date>2014-08-24T05:21:40Z</date>
    <key>Application Version</key><string>11.3.1</string>
    <key>Features</key><integer>5</integer>
    <key>Show Content Ratings</key><true/>
    <key>Music Folder</key><string>file://localhost/C:/Users/Mon%20Tolentino/Music/iTunes/iTunes%20Media/</string>
    <key>Library Persistent ID</key><string>15CDC06EC711077D</string>
    <key>Tracks</key>
    <dict>
        <key>766</key>
        <dict>
            <key>Track ID</key><integer>766</integer>
            <key>Name</key><string>Say Something</string>
            <key>Artist</key><string>A Great Big World</string>
            <key>Album Artist</key><string>A Great Big World</string>
            <key>Composer</key><string>Ian Axel, Chad Vaccarino, Mike Campbell</string>
            <key>Album</key><string>Is There Anybody Out There?</string>
            <key>Grouping</key><string>Indie</string>
            <key>Genre</key><string>Pop</string>
            <key>Kind</key><string>AAC audio file</string>
            <key>Size</key><integer>8639959</integer>
            <key>Total Time</key><integer>233289</integer>
            <key>Disc Number</key><integer>1</integer>
            <key>Disc Count</key><integer>1</integer>
            <key>Track Number</key><integer>5</integer>
            <key>Track Count</key><integer>13</integer>
            <key>Year</key><integer>2013</integer>
            <key>BPM</key><integer>94</integer>
            <key>Date Modified</key><date>2014-05-25T15:58:35Z</date>
            <key>Date Added</key><date>2014-05-18T10:09:13Z</date>
            <key>Bit Rate</key><integer>256</integer>
            <key>Sample Rate</key><integer>44100</integer>
            <key>Play Count</key><integer>33</integer>
            <key>Play Date</key><integer>3491589574</integer>
            <key>Play Date UTC</key><date>2014-08-22T13:59:34Z</date>
            <key>Skip Count</key><integer>7</integer>
            <key>Skip Date</key><date>2014-08-15T15:15:43Z</date>
            <key>Release Date</key><date>2013-11-04T12:00:00Z</date>
            <key>Rating</key><integer>60</integer>
            <key>Album Rating</key><integer>60</integer>
            <key>Album Rating Computed</key><true/>
            <key>Artwork Count</key><integer>1</integer>
            <key>Sort Album Artist</key><string>A Great Big World</string>
            <key>Sort Artist</key><string>A Great Big World</string>
            <key>Persistent ID</key><string>50A143EFFA8BEA97</string>
            <key>Track Type</key><string>File</string>
            <key>Location</key><string>file://localhost/C:/Users/Mon%20Tolentino/Music/iTunes/iTunes%20Media/Music/A%20Great%20Big%20World/Is%20There%20Anybody%20Out%20There_/05%20Say%20Something.m4a</string>
            <key>File Folder Count</key><integer>5</integer>
            <key>Library Folder Count</key><integer>1</integer>
        </dict>

我在网上找到的:

    Dim itunesLib As XElement = XElement.Load("xmllocation")

    Dim itunesPlaylists = From key In itunesLib...<key> Where key.Value = "Name"
                          Select key.ElementsAfterSelf("string").Value

    List1.ItemsSource = itunesPlaylists

但它只在列表框中列出了我所有的轨道，谁能帮帮我。

Answer 1

哇，这是我见过的最糟糕的 XML。对于不得不忍受这一点，我深表歉意。

我很想从将它们解析为具体类的(可能是延迟的)集合开始，然后是 .Where那些找到你要找的人。

我最初是用 C# 编写所有这些代码的，因为我实际上并不真正了解 VB，然后使用在线工具对其进行了转换，所以请告诉我这是否存在问题或者是否有任何不是最佳实践。不过，它应该传达工作流程的要点，这才是真正的重点。

那么，我将从编写一个类开始:

Public Class Track
    Public Property Name() As String
        Get
            Return m_Name
        End Get
        Set
            m_Name = Value
        End Set
    End Property
    Private m_Name As String
    Public Property Explicit() As Boolean
        Get
            Return m_Explicit
        End Get
        Set
            m_Explicit = Value
        End Set
    End Property
    Private m_Explicit As Boolean
End Class

然后我会编写一个方法来获取 <dict> 中任何键的值元素

Private Function GetValue(Of T)(dict As XElement, key As String) As T
    Dim element = dict.Elements("key").FirstOrDefault(Function(c) String.Equals(DirectCast(c, String), key))

    If element Is Nothing OrElse element.NextNode Is Nothing Then
        Return Nothing
    End If

    element = element.NextNode

    If T = GetType(Boolean) Then
        Return element.Name = "true"
    Else
        Return DirectCast(element, T)
    End If
End Function

然后将 XML 解析为该类:

Dim root = XElement.Load(path)

root = root.Element("dict")

Dim tracks = root.Elements("key").First(Function(c) DirectCast(c, String) = "Tracks").NextNode.Elements("dict")

Dim parsedTracks As IEnumerable(Of Track) = tracks.[Select](Function(c) New Track() With { _
    Key .Name = GetValue(Of String)(c, "Name"), _
    Key .Explicit = GetValue(Of Boolean)(c, "Explicit") _
})

然后你可以很容易地查询:

Return parsedTracks.First(Function(c) c.Name = desiredTrackName).Explicit

我敢肯定，您会想要添加很多错误处理，但这应该传达了一种好的处理方式的要点。您可能想要也可能不想投入 .ToArray()在那里打电话。这真的取决于你如何使用它。这将，就目前而言，每次调用只循环一次(因此“延迟”)，所以如果您不经常进行搜索，那很好。但你可能想要 .ToArray()以便它全部加载到内存中，并且如果您进行更多调用则已经解析。