如何在使用<x>而不是<x> </x> </x>时反序列化空XML元素

时间：2013-12-19 19:38:12

标签： xml vb.net xsd2code

我有一个XSD架构和XML文件，用于在运行时构建组件。这些对象可以具有自定义设置。在XSD文件中，这被定义为：

<xs:complexType name="ComponentSettings">
  <xs:sequence>
    <xs:any minOccurs="0"/>
  </xs:sequence>
</xs:complexType>

并在XSD中实例化为：

<xs:complexType name="Component">
  <xs:sequence>
    <xs:element name="Version" type="VersionRecord"/>
    <xs:element name="Settings" type="ComponentSettings"/>
  </xs:sequence>
  <xs:attribute name="Name" type="xs:string" use="required"/>
</xs:complexType>

在反序列化XML文件时遇到一个有趣的问题。如果我有一个没有设置的组件，XML看起来像这样：

<Settings></Settings>

我没有问题。

但是，如果XML看起来像这样：

<Settings/>

然后反序列化将在此标记之后无声地失败，并且我最终得到一条不完整的记录。

我正在使用xsd2code生成的以下代码：

<System.CodeDom.Compiler.GeneratedCodeAttribute("System.Xml", "4.0.30319.18060"), _
 System.SerializableAttribute(), _
 System.ComponentModel.DesignerCategoryAttribute("code"), _
 System.Xml.Serialization.XmlRootAttribute([Namespace]:="", IsNullable:=True)> _
Partial Public Class Component
    Implements System.ComponentModel.INotifyPropertyChanged

    Private versionField As VersionRecord

    Private settingsField As System.Xml.XmlElement

    Private nameField As String

    Private Shared sSerializer As System.Xml.Serialization.XmlSerializer

    '''<summary>
    '''Component class constructor
    '''</summary>
    Public Sub New()
        MyBase.New()
        Me.versionField = New VersionRecord()
    End Sub

    <System.Xml.Serialization.XmlElementAttribute(Order:=0)> _
    Public Property Version() As VersionRecord
        Get
            Return Me.versionField
        End Get
        Set(value As VersionRecord)
            If (Not (Me.versionField) Is Nothing) Then
                If (versionField.Equals(value) <> True) Then
                    Me.versionField = value
                    Me.OnPropertyChanged("Version")
                End If
            Else
                Me.versionField = value
                Me.OnPropertyChanged("Version")
            End If
        End Set
    End Property

    <System.Xml.Serialization.XmlElementAttribute(Order:=2)> _
    Public Property Settings() As System.Xml.XmlElement
        Get
            Return Me.settingsField
        End Get
        Set(value As System.Xml.XmlElement)
            If (Not (Me.settingsField) Is Nothing) Then
                If (settingsField.Equals(value) <> True) Then
                    Me.settingsField = value
                    Me.OnPropertyChanged("Settings")
                End If
            Else
                Me.settingsField = value
                Me.OnPropertyChanged("Settings")
            End If
        End Set
    End Property

    <System.Xml.Serialization.XmlAttributeAttribute()> _
    Public Property Name() As String
        Get
            Return Me.nameField
        End Get
        Set(value As String)
            If (Not (Me.nameField) Is Nothing) Then
                If (nameField.Equals(value) <> True) Then
                    Me.nameField = value
                    Me.OnPropertyChanged("Name")
                End If
            Else
                Me.nameField = value
                Me.OnPropertyChanged("Name")
            End If
        End Set
    End Property

#Region "Serialize/Deserialize"
    '''<summary>
    '''Serializes current Component object into an XML document
    '''</summary>
    '''<returns>string XML value</returns>
    Public Overridable Overloads Function Serialize(ByVal encoding As System.Text.Encoding) As String
        Dim streamReader As System.IO.StreamReader = Nothing
        Dim memoryStream As System.IO.MemoryStream = Nothing
        Try
            memoryStream = New System.IO.MemoryStream()
            Dim xmlWriterSettings As System.Xml.XmlWriterSettings = New System.Xml.XmlWriterSettings()
            xmlWriterSettings.Encoding = encoding
            Dim xmlWriter As System.Xml.XmlWriter = xmlWriter.Create(memoryStream, xmlWriterSettings)
            Serializer.Serialize(xmlWriter, Me)
            memoryStream.Seek(0, System.IO.SeekOrigin.Begin)
            streamReader = New System.IO.StreamReader(memoryStream)
            Return streamReader.ReadToEnd
        Finally
            If (Not (streamReader) Is Nothing) Then
                streamReader.Dispose()
            End If
            If (Not (memoryStream) Is Nothing) Then
                memoryStream.Dispose()
            End If
        End Try
    End Function

    Public Overridable Overloads Function Serialize() As String
        Return Serialize(Encoding.UTF8)
    End Function

    '''<summary>
    '''Deserializes workflow markup into an Component object
    '''</summary>
    '''<param name="xml">string workflow markup to deserialize</param>
    '''<param name="obj">Output Component object</param>
    '''<param name="exception">output Exception value if deserialize failed</param>
    '''<returns>true if this XmlSerializer can deserialize the object; otherwise, false</returns>
    Public Overloads Shared Function Deserialize(ByVal xml As String, ByRef obj As Component, ByRef exception As System.Exception) As Boolean
        exception = Nothing
        obj = CType(Nothing, Component)
        Try
            obj = Deserialize(xml)
            Return True
        Catch ex As System.Exception
            exception = ex
            Return False
        End Try
    End Function

    Public Overloads Shared Function Deserialize(ByVal xml As String, ByRef obj As Component) As Boolean
        Dim exception As System.Exception = Nothing
        Return Deserialize(xml, obj, exception)
    End Function

    Public Overloads Shared Function Deserialize(ByVal xml As String) As Component
        Dim stringReader As System.IO.StringReader = Nothing
        Try
            stringReader = New System.IO.StringReader(xml)
            Return CType(Serializer.Deserialize(System.Xml.XmlReader.Create(stringReader)), Component)
        Finally
            If (Not (stringReader) Is Nothing) Then
                stringReader.Dispose()
            End If
        End Try
    End Function

    '''<summary>
    '''Serializes current Component object into file
    '''</summary>
    '''<param name="fileName">full path of outupt xml file</param>
    '''<param name="exception">output Exception value if failed</param>
    '''<returns>true if can serialize and save into file; otherwise, false</returns>
    Public Overridable Overloads Function SaveToFile(ByVal fileName As String, ByVal encoding As System.Text.Encoding, ByRef exception As System.Exception) As Boolean
        exception = Nothing
        Try
            SaveToFile(fileName, encoding)
            Return True
        Catch e As System.Exception
            exception = e
            Return False
        End Try
    End Function

    Public Overridable Overloads Function SaveToFile(ByVal fileName As String, ByRef exception As System.Exception) As Boolean
        Return SaveToFile(fileName, Encoding.UTF8, exception)
    End Function

    Public Overridable Overloads Sub SaveToFile(ByVal fileName As String)
        SaveToFile(fileName, Encoding.UTF8)
    End Sub

    Public Overridable Overloads Sub SaveToFile(ByVal fileName As String, ByVal encoding As System.Text.Encoding)
        Dim streamWriter As System.IO.StreamWriter = Nothing
        Try
            Dim xmlString As String = Serialize(encoding)
            streamWriter = New System.IO.StreamWriter(fileName, False, encoding.UTF8)
            streamWriter.WriteLine(xmlString)
            streamWriter.Close()
        Finally
            If (Not (streamWriter) Is Nothing) Then
                streamWriter.Dispose()
            End If
        End Try
    End Sub

    '''<summary>
    '''Deserializes xml markup from file into an Component object
    '''</summary>
    '''<param name="fileName">string xml file to load and deserialize</param>
    '''<param name="obj">Output Component object</param>
    '''<param name="exception">output Exception value if deserialize failed</param>
    '''<returns>true if this XmlSerializer can deserialize the object; otherwise, false</returns>
    Public Overloads Shared Function LoadFromFile(ByVal fileName As String, ByVal encoding As System.Text.Encoding, ByRef obj As Component, ByRef exception As System.Exception) As Boolean
        exception = Nothing
        obj = CType(Nothing, Component)
        Try
            obj = LoadFromFile(fileName, encoding)
            Return True
        Catch ex As System.Exception
            exception = ex
            Return False
        End Try
    End Function

    Public Overloads Shared Function LoadFromFile(ByVal fileName As String, ByRef obj As Component, ByRef exception As System.Exception) As Boolean
        Return LoadFromFile(fileName, Encoding.UTF8, obj, exception)
    End Function

    Public Overloads Shared Function LoadFromFile(ByVal fileName As String, ByRef obj As Component) As Boolean
        Dim exception As System.Exception = Nothing
        Return LoadFromFile(fileName, obj, exception)
    End Function

    Public Overloads Shared Function LoadFromFile(ByVal fileName As String) As Component
        Return LoadFromFile(fileName, Encoding.UTF8)
    End Function

    Public Overloads Shared Function LoadFromFile(ByVal fileName As String, ByVal encoding As System.Text.Encoding) As Component
        Dim file As System.IO.FileStream = Nothing
        Dim sr As System.IO.StreamReader = Nothing
        Try
            file = New System.IO.FileStream(fileName, FileMode.Open, FileAccess.Read)
            sr = New System.IO.StreamReader(file, encoding)
            Dim xmlString As String = sr.ReadToEnd
            sr.Close()
            file.Close()
            Return Deserialize(xmlString)
        Finally
            If (Not (file) Is Nothing) Then
                file.Dispose()
            End If
            If (Not (sr) Is Nothing) Then
                sr.Dispose()
            End If
        End Try
    End Function
#End Region

#Region "Clone method"
    '''<summary>
    '''Create a clone of this Component object
    '''</summary>
    Public Overridable Function Clone() As Component
        Return CType(Me.MemberwiseClone, Component)
    End Function
#End Region
End Class

我很好奇为什么会这样，以及是否有办法不体验这一点。

2 个答案:

答案 0 :(得分：0)

＆LT;设置＆gt;＆LT; /设置＆gt;和＆lt;设置/＆gt;在XML中语义相同。如果您的代码对一个代码的响应不同，那么代码就会被破坏。

答案 1 :(得分：0)

Per http://msdn.microsoft.com/en-us/library/system.xml.xmlreader.isemptyelement%28v=vs.110%29.aspx，“不为空元素生成相应的EndElement节点。”

似乎微软公然无视XML标准，故意对待这两种情况。

我创建了以下方法来修补XML文本：

        Public Function XMLReaderPatch(rawXML As String) As String
            If String.IsNullOrEmpty(rawXML) Then Return rawXML

            'Pattern for finding items similar to <name*/> where * may represent whitespace followed by text and/or whitespace
            Dim pattern As String = "<(\S+)(\s[^<|>]*)?/>"
            'Pattern for replacing with items similar to <name*></name> where * may represent whitespace followed by text and/or whitespace
            Dim replacement As String = "<$1$2></$1>"
            Dim rgx As New Text.RegularExpressions.Regex(pattern)

            Return rgx.Replace(rawXML, replacement)
        End Function
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