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XmlValueGetter Delegate

A delegate used by the XmlSchemaValidator class to pass attribute, text, and white space values as a Common Language Runtime (CLR) type compatible with the XML Schema Definition Language (XSD) type of the attribute, text, or white space.

Namespace: System.Xml.Schema
Assembly: System.Xml (in system.xml.dll)

Public Delegate Function XmlValueGetter () As Object
Dim instance As New XmlValueGetter(AddressOf HandlerMethod)
/** @delegate */
public delegate Object XmlValueGetter ()
Not applicable.

Return Value

An object containing the attribute, text, or white space value. The object is a CLR type that that corresponds to the XSD type of the attribute, text, or white space value.

An XmlValueGetterdelegate is useful if the CLR value of an attribute, text, or white space node is already available, and avoids the cost of converting it to a string and then reparsing it again for validation.

For more information about the XmlSchemaValidator class, see the XmlSchemaValidator Push-Based Validation topic, or the XmlSchemaValidator class reference documentation.

The following example validates the contosoBooks.xml file against the contosoBooks.xsd schema. The example uses the XmlSerializer class to deserialize the contosoBooks.xml file and pass the value of the nodes to the methods of the XmlSchemaValidator class.

Imports System
Imports System.Xml
Imports System.Xml.Schema
Imports System.Xml.Serialization

Namespace Microsoft.Samples.Xml.Schema

    Class XmlSchemaValidatorExamples

        Shared Sub Main()

            ' The XML document to deserialize into the XmlSerializer object.
            Dim reader As XmlReader = XmlReader.Create("contosoBooks.xml")

            ' The XmlSerializer object.
            Dim serializer As XmlSerializer = New XmlSerializer(GetType(ContosoBooks))
            Dim books As ContosoBooks = CType(serializer.Deserialize(reader), ContosoBooks)

            ' The XmlSchemaSet object containing the schema used to validate the XML document.
            Dim schemaSet As XmlSchemaSet = New XmlSchemaSet()
            schemaSet.Add("", "contosoBooks.xsd")

            ' The XmlNamespaceManager object used to handle namespaces.
            Dim manager As XmlNamespaceManager = New XmlNamespaceManager(reader.NameTable)

            ' Assign a ValidationEventHandler to handle schema validation warnings and errors.
            Dim validator As XmlSchemaValidator = New XmlSchemaValidator(reader.NameTable, schemaSet, manager, XmlSchemaValidationFlags.None)
            'validator.ValidationEventHandler += New ValidationEventHandler(SchemaValidationEventHandler)
            AddHandler validator.ValidationEventHandler, AddressOf SchemaValidationEventHandler

            ' Initialize the XmlSchemaValidator object.

            ' Validate the bookstore element, verify that all required attributes are present
            ' and prepare to validate child content.
            validator.ValidateElement("bookstore", "", Nothing)

            ' Get the next exptected element in the bookstore context.
            Dim particles() As XmlSchemaParticle = validator.GetExpectedParticles()
            Dim nextElement As XmlSchemaElement = particles(0)
            Console.WriteLine("Expected Element: '{0}'", nextElement.Name)

            For Each book As BookType In
                ' Validate the book element.
                validator.ValidateElement("book", "", Nothing)

                ' Get the exptected attributes for the book element.
                Console.Write(vbCrLf & "Expected attributes: ")
                Dim attributes() As XmlSchemaAttribute = validator.GetExpectedAttributes()
                For Each attribute As XmlSchemaAttribute In attributes
                    Console.Write("'{0}' ", attribute.Name)

                ' Validate the genre attribute and display it's post schema validation information.
                If Not book.Genre Is Nothing Then
                    validator.ValidateAttribute("genre", "", book.Genre, schemaInfo)
                End If

                ' Validate the publicationdate attribute and display it's post schema validation information.
                If Not book.PublicationDate = Nothing Then
                    validator.ValidateAttribute("publicationdate", "", dateTimeGetter(book.PublicationDate), schemaInfo)
                End If

                ' Validate the ISBN attribute and display it's post schema validation information.
                If Not book.Isbn Is Nothing Then
                    validator.ValidateAttribute("ISBN", "", book.Isbn, schemaInfo)
                End If

                ' Verify that all required attributes of the book element are present
                ' and prepare to validate child content.

                ' Validate the title element and it's content.
                validator.ValidateElement("title", "", Nothing)
                validator.ValidateEndElement(Nothing, book.Title)

                ' Validate the author element, verify that all required attributes are present
                ' and prepare to validate child content.
                validator.ValidateElement("author", "", Nothing)

                If Not book.Author.Name Is Nothing Then
                    ' Validate the name element and it's content.
                    validator.ValidateElement("name", "", Nothing)
                    validator.ValidateEndElement(Nothing, book.Author.Name)
                End If

                If Not book.Author.FirstName Is Nothing Then
                    ' Validate the first-name element and it's content.
                    validator.ValidateElement("first-name", "", Nothing)
                    validator.ValidateEndElement(Nothing, book.Author.FirstName)

                End If

                If Not book.Author.LastName Is Nothing Then
                    ' Validate the last-name element and it's content.
                    validator.ValidateElement("last-name", "", Nothing)
                    validator.ValidateEndElement(Nothing, book.Author.LastName)
                End If

                ' Validate the content of the author element.

                ' Validate the price element and it's content.
                validator.ValidateElement("price", "", Nothing)
                validator.ValidateEndElement(Nothing, book.Price)

                ' Validate the content of the book element.

            ' Validate the content of the bookstore element.

            ' Close the XmlReader object.

        End Sub

        Shared schemaInfo As XmlSchemaInfo = New XmlSchemaInfo()
        Shared dateTimeGetterContent As Object

        Shared Function dateTimeGetterHandle() As Object

            Return dateTimeGetterContent

        End Function

        Shared Function dateTimeGetter(ByVal dateTime As DateTime) As XmlValueGetter

            dateTimeGetterContent = dateTime
            Return New XmlValueGetter(AddressOf dateTimeGetterHandle)

        End Function

        Shared Sub DisplaySchemaInfo()

            If Not schemaInfo.SchemaElement Is Nothing Then
                Console.WriteLine("Element '{0}' with type '{1}' is '{2}'", schemaInfo.SchemaElement.Name, schemaInfo.SchemaType, schemaInfo.Validity)
            ElseIf Not schemaInfo.SchemaAttribute Is Nothing Then
                Console.WriteLine("Attribute '{0}' with type '{1}' is '{2}'", schemaInfo.SchemaAttribute.Name, schemaInfo.SchemaType, schemaInfo.Validity)
            End If

        End Sub

        Shared Sub SchemaValidationEventHandler(ByVal sender As Object, ByVal e As ValidationEventArgs)

            Select Case e.Severity
                Case XmlSeverityType.Error
                    Console.WriteLine(vbCrLf & "Error: {0}", e.Message)
                    Exit Sub
                Case XmlSeverityType.Warning
                    Console.WriteLine(vbCrLf & "Warning: {0}", e.Message)
                    Exit Sub
            End Select

        End Sub

    End Class

    <XmlRootAttribute("bookstore", Namespace:="", IsNullable:=False)> _
    Public Class ContosoBooks

        <XmlElementAttribute("book")> _
        Public book() As BookType

    End Class

    Public Class BookType

        <XmlAttributeAttribute("genre")> _
        Public Genre As String

        <XmlAttributeAttribute("publicationdate", DataType:="date")> _
        Public PublicationDate As DateTime

        <XmlAttributeAttribute("ISBN")> _
        Public Isbn As String

        <XmlElementAttribute("title")> _
        Public Title As String

        <XmlElementAttribute("author")> _
        Public Author As BookAuthor

        <XmlElementAttribute("price")> _
        Public Price As Decimal

    End Class

    Public Class BookAuthor

        <XmlElementAttribute("name")> _
        Public Name As String

        <XmlElementAttribute("first-name")> _
        Public FirstName As String

        <XmlElementAttribute("last-name")> _
        Public LastName As String

    End Class

End Namespace

The example takes the contosoBooks.xml file as input.

<bookstore xmlns="">
    <book genre="autobiography" publicationdate="1981-03-22" ISBN="1-861003-11-0">
        <title>The Autobiography of Benjamin Franklin</title>
    <book genre="novel" publicationdate="1967-11-17" ISBN="0-201-63361-2">
        <title>The Confidence Man</title>
    <book genre="philosophy" publicationdate="1991-02-15" ISBN="1-861001-57-6">
        <title>The Gorgias</title>

The example also takes the contosoBooks.xsd as an input.

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="" xmlns:xs="">
    <xs:element name="bookstore">
                <xs:element maxOccurs="unbounded" name="book">
                            <xs:element name="title" type="xs:string" />
                            <xs:element name="author">
                                        <xs:element minOccurs="0" name="name" type="xs:string" />
                                        <xs:element minOccurs="0" name="first-name" type="xs:string" />
                                        <xs:element minOccurs="0" name="last-name" type="xs:string" />
                            <xs:element name="price" type="xs:decimal" />
                        <xs:attribute name="genre" type="xs:string" use="required" />
                        <xs:attribute name="publicationdate" type="xs:date" use="required" />
                        <xs:attribute name="ISBN" type="xs:string" use="required" />

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0