XmlDocument.Validate Method (ValidationEventHandler)

 

Validates the XmlDocument against the XML Schema Definition Language (XSD) schemas contained in the Schemas property.

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

Public Sub Validate (
	validationEventHandler As ValidationEventHandler
)

Parameters

validationEventHandler
Type: System.Xml.Schema.ValidationEventHandler

The ValidationEventHandler object that receives information about schema validation warnings and errors.

Exception Condition
XmlSchemaValidationException

A schema validation event occurred and no ValidationEventHandler object was specified.

The Validate method validates the XML data in the XmlDocument against the schemas contained in the Schemas property. The Validate method performs infoset augmentation. Specifically, after successful validation, schema defaults are applied, text values are converted to atomic values as necessary, and type information is associated with validated information items. The result is a previously un-typed XML sub-tree in the XmlDocument replaced with a typed sub-tree.

The following are important notes to consider when using the Validate method.

  • Schema location hints like xsi:schemaLocation or xsi:noNamespaceSchemaLocation are ignored.

  • Inline schemas are ignored.

  • If schema validation errors occur during validation the XmlDocument becomes partially validated with some nodes with correct type information and some without.

  • The validation process includes checking for uniqueness and reference constraints (xs:ID, xs:IDREF, xs:key, xs:keyref, and xs:unique).

The following example illustrates use of the Validate method. The example creates an XmlDocument that contains an associated XSD schema using the XmlReaderSettings and XmlReader objects. The example then uses the XPathNavigator class to incorrectly modify the typed value of an element in the XML document generating a schema validation error.

Imports System
Imports System.Xml
Imports System.Xml.Schema
Imports System.Xml.XPath

Class XPathValidation

    Shared Sub Main()

        Try

            Dim settings As XmlReaderSettings = New XmlReaderSettings()
            settings.Schemas.Add("http://www.contoso.com/books", "contosoBooks.xsd")
            settings.ValidationType = ValidationType.Schema

            Dim reader As XmlReader = XmlReader.Create("contosoBooks.xml", settings)
            Dim document As XmlDocument = New XmlDocument()
            document.Load(reader)

            Dim eventHandler As ValidationEventHandler = New ValidationEventHandler(AddressOf ValidationEventHandler)

            ' the following call to Validate succeeds.
            document.Validate(eventHandler)

            ' add a node so that the document is no longer valid
            Dim navigator As XPathNavigator = document.CreateNavigator()
            navigator.MoveToFollowing("price", "http://www.contoso.com/books")
            Dim writer As XmlWriter = navigator.InsertAfter()
            writer.WriteStartElement("anotherNode", "http://www.contoso.com/books")
            writer.WriteEndElement()
            writer.Close()

            ' the document will now fail to successfully validate
            document.Validate(eventHandler)

        Catch ex As Exception

            Console.WriteLine(ex.Message)

        End Try

    End Sub

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

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

    End Sub

End Class

The example takes the contosoBooks.xml and contosoBooks.xsd files as input.

<?xml version="1.0" encoding="utf-8" ?>
<bookstore xmlns="http://www.contoso.com/books">
    <book genre="autobiography" publicationdate="1981-03-22" ISBN="1-861003-11-0">
        <title>The Autobiography of Benjamin Franklin</title>
        <author>
            <first-name>Benjamin</first-name>
            <last-name>Franklin</last-name>
        </author>
        <price>8.99</price>
    </book>
    <book genre="novel" publicationdate="1967-11-17" ISBN="0-201-63361-2">
        <title>The Confidence Man</title>
        <author>
            <first-name>Herman</first-name>
            <last-name>Melville</last-name>
        </author>
        <price>11.99</price>
    </book>
    <book genre="philosophy" publicationdate="1991-02-15" ISBN="1-861001-57-6">
        <title>The Gorgias</title>
        <author>
            <name>Plato</name>
        </author>
        <price>9.99</price>
    </book>
</bookstore>
<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.contoso.com/books" xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="bookstore">
        <xs:complexType>
            <xs:sequence>
                <xs:element maxOccurs="unbounded" name="book">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="title" type="xs:string" />
                            <xs:element name="author">
                                <xs:complexType>
                                    <xs:sequence>
                                        <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:sequence>
                                </xs:complexType>
                            </xs:element>
                            <xs:element name="price" type="xs:decimal" />
                        </xs:sequence>
                        <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" />
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

.NET Framework
Available since 2.0
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