XmlValidatingReader.ReadAttributeValue Method ()

 

Parses the attribute value into one or more Text, EntityReference, or EndEntity nodes.

Namespace:   System.Xml
Assembly:  System.Xml (in System.Xml.dll)

Public Overrides Function ReadAttributeValue As Boolean

Return Value

Type: System.Boolean

true if there are nodes to return.

false if the reader is not positioned on an attribute node when the initial call is made or if all the attribute values have been read.

An empty attribute, such as, misc="", returns true with a single node with a value of String.Empty.

System_CAPS_noteNote

The XmlValidatingReader class is obsolete in .NET Framework 2.0. You can create a validating XmlReader instance by using the XmlReaderSettings class and the Create method. For more information, see the Remarks section of the XmlReader reference page.

Use this method after calling MoveToAttribute to read through the text or entity reference nodes that make up the attribute value. The Depth of the attribute value nodes is one plus the depth of the attribute node. The Depth increments and decrements by one when you step into and out of general entity references.

For example, suppose you have the following XML: <test name="a &b; c"/>

where the entity b is defined in the document type definition (DTD) as follows: <!ENTITY b "123">

If EntityHandling is set to ExpandCharEntities, the following C# code returns the attribute value as two text nodes and one entity reference node:

reader.MoveToAttribute("name");
  while (reader.ReadAttributeValue())
  {
  if (reader.NodeType == XmlNodeType.Text)
  {
  // at this point reader.Value == "a " or " c"
  }
  else if (reader.NodeType == XmlNodeType.EntityReference)
  {
  // at this point reader.Name == "b"
  reader.ResolveEntity();
  while (reader.ReadAttributeValue() &&
  reader.NodeType != XmlNodeType.EndEntity)
  {
  // reader.Value == "123"
  }
  }
    }

The following example reads an attribute with text and entity reference nodes.

Option Strict
Option Explicit

Imports System
Imports System.IO
Imports System.Xml

Public Class Sample

    Public Shared Sub Main()
        Dim reader As XmlValidatingReader = Nothing

        Try
            'Create the XML fragment to be parsed.
            Dim xmlFrag As String = "<book genre='novel' misc='sale-item &h; 1987'></book>"

            'Create the XmlParserContext.
            Dim context As XmlParserContext
            Dim subset As String = "<!ENTITY h 'hardcover'>"
            context = New XmlParserContext(Nothing, Nothing, "book", Nothing, Nothing, subset, "", "", XmlSpace.None)

            'Create the reader and set it to not expand general entities. 
            reader = New XmlValidatingReader(xmlFrag, XmlNodeType.Element, context)
            reader.ValidationType = ValidationType.None
            reader.EntityHandling = EntityHandling.ExpandCharEntities

            'Read the misc attribute. Because EntityHandling is set to
            'ExpandCharEntities, the attribute is parsed into multiple text
            'and entity reference nodes.
            reader.MoveToContent()
            reader.MoveToAttribute("misc")
            While reader.ReadAttributeValue()
                If reader.NodeType = XmlNodeType.EntityReference Then
                    'To expand the entity, call ResolveEntity.
                    Console.WriteLine("{0} {1}", reader.NodeType, reader.Name)
                Else
                    Console.WriteLine("{0} {1}", reader.NodeType, reader.Value)
                End If
            End While
        Finally
            If Not (reader Is Nothing) Then
                reader.Close()
            End If
        End Try
    End Sub 'Main
End Class 'Sample 

.NET Framework
Available since 1.1
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