XML documents can be validated against an XML schema definition language (XSD) schema in an XmlSchemaSet.
Validate XML documents
XML documents are validated by the Create method of the XmlReader class. To validate an XML document, construct an XmlReaderSettings object that contains an XML schema definition language (XSD) schema with which to validate the XML document.
An individual schema or a set of schemas (as an XmlSchemaSet) can be added to an XmlSchemaSet by passing either one as a parameter to the Add method of XmlSchemaSet. When validating a document the target namespace of the document must match the target namespace of the schema in the schema set.
The following is an example XML document.
<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>
The following is the schema that validates the example XML document.
<?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>
In the code example that follows, the schema above is added to the Schemas property of the XmlReaderSettings object. The XmlReaderSettings object is passed as a parameter to the Create method of the XmlReader object, which validates the XML document above.
The ValidationType property of the XmlReaderSettings object is set to Schema to enforce validation of the XML document by the Create method of the XmlReader object. A ValidationEventHandler is added to the XmlReaderSettings object to handle any Warning or Error events raised by errors found during the validation process of both the XML document and the schema.
using System;
using System.Xml;
using System.Xml.Schema;
class XmlSchemaSetExample
{
static void Main()
{
XmlReaderSettings booksSettings = new XmlReaderSettings();
booksSettings.Schemas.Add("http://www.contoso.com/books", "books.xsd");
booksSettings.ValidationType = ValidationType.Schema;
booksSettings.ValidationEventHandler += booksSettingsValidationEventHandler;
XmlReader books = XmlReader.Create("books.xml", booksSettings);
while (books.Read()) { }
}
static void booksSettingsValidationEventHandler(object sender, ValidationEventArgs e)
{
if (e.Severity == XmlSeverityType.Warning)
{
Console.Write("WARNING: ");
Console.WriteLine(e.Message);
}
else if (e.Severity == XmlSeverityType.Error)
{
Console.Write("ERROR: ");
Console.WriteLine(e.Message);
}
}
}
Imports System.Xml
Imports System.Xml.Schema
Class XmlSchemaSetExample
Shared Sub Main()
Dim booksSettings As XmlReaderSettings = New XmlReaderSettings()
booksSettings.Schemas.Add("http://www.contoso.com/books", "books.xsd")
booksSettings.ValidationType = ValidationType.Schema
AddHandler booksSettings.ValidationEventHandler, New ValidationEventHandler(AddressOf booksSettingsValidationEventHandler)
Dim books As XmlReader = XmlReader.Create("books.xml", booksSettings)
While books.Read()
End While
End Sub
Shared Sub booksSettingsValidationEventHandler(ByVal sender As Object, ByVal e As ValidationEventArgs)
If e.Severity = XmlSeverityType.Warning Then
Console.Write("WARNING: ")
Console.WriteLine(e.Message)
ElseIf e.Severity = XmlSeverityType.Error Then
Console.Write("ERROR: ")
Console.WriteLine(e.Message)
End If
End Sub
End Class