Validation Using the XmlSchemaSet

The XmlSchemaSet is a cache or library where the XML Schema definition language (XSD) schemas can be stored. XmlSchemaSet improves performance by caching schemas in memory instead of accessing them from a file or a URL. Each schema in the XmlSchemaSet is identified by the namespace URI and schema location specified when then schema was added to the XmlSchemaSet. The Schemas property assigns the XmlSchemaSet object to use.

Example

The following example validates an XML file using schemas stored in the XmlSchemaSet. The namespace in the XML file, urn:bookstore-schema, identifies which schema in the XmlSchemaSet to use for validation.

Imports System
Imports System.Xml
Imports System.Xml.Schema
Imports System.IO

public class Sample 

  public shared sub Main() 

    ' Create the XmlSchemaSet class.
    Dim sc as XmlSchemaSet = new XmlSchemaSet()

    ' Add the schema to the collection.
    sc.Add("urn:bookstore-schema", "books.xsd")

    ' Set the validation settings.
    Dim settings as XmlReaderSettings = new XmlReaderSettings()
    settings.ValidationType = ValidationType.Schema
    settings.Schemas = sc
    AddHandler settings.ValidationEventHandler, AddressOf ValidationCallBack

    ' Create the XmlReader object.
    Dim reader as XmlReader = XmlReader.Create("booksSchemaFail.xml", settings)

    ' Parse the file. 
    while reader.Read()
    end while

  end sub

  ' Display any validation errors.
  private shared sub ValidationCallBack(sender as object, e as ValidationEventArgs) 
    Console.WriteLine("Validation Error: {0}", e.Message)
  end sub
end class

using System;
using System.Xml;
using System.Xml.Schema;
using System.IO;

public class Sample {

  public static void Main() {

    // Create the XmlSchemaSet class.
    XmlSchemaSet sc = new XmlSchemaSet();

    // Add the schema to the collection.
    sc.Add("urn:bookstore-schema", "books.xsd");

    // Set the validation settings.
    XmlReaderSettings settings = new XmlReaderSettings();
    settings.ValidationType = ValidationType.Schema;
    settings.Schemas = sc;
    settings.ValidationEventHandler += new ValidationEventHandler (ValidationCallBack);

    // Create the XmlReader object.
    XmlReader reader = XmlReader.Create("booksSchemaFail.xml", settings);

    // Parse the file. 
    while (reader.Read());

  }

  // Display any validation errors.
  private static void ValidationCallBack(object sender, ValidationEventArgs e) {
    Console.WriteLine("Validation Error: {0}", e.Message);
  }
}

#using <System.Xml.dll>

using namespace System;
using namespace System::Xml;
using namespace System::Xml::Schema;
using namespace System::IO;

// Display any validation errors.
static void ValidationCallBack( Object^ /*sender*/, ValidationEventArgs^ e )
{
   Console::WriteLine( L"Validation Error: {0}", e->Message );
}

int main()
{
   // Create the XmlSchemaSet class.
   XmlSchemaSet^ sc = gcnew XmlSchemaSet;

   // Add the schema to the collection.
   sc->Add( L"urn:bookstore-schema", L"books.xsd" );

   // Set the validation settings.
   XmlReaderSettings^ settings = gcnew XmlReaderSettings;
   settings->ValidationType = ValidationType::Schema;
   settings->Schemas = sc;
   settings->ValidationEventHandler += gcnew ValidationEventHandler( ValidationCallBack );

   // Create the XmlReader object.
   XmlReader^ reader = XmlReader::Create( L"booksSchemaFail.xml", settings );

   // Parse the file. 
   while ( reader->Read() )
      ;

   return 1;
}

Input

The sample uses the following two input files.

booksSchemaFail.xml

<?xml version='1.0'?>
<bookstore xmlns="urn:bookstore-schema">
  <book>
    <author>
      <first-name>Benjamin</first-name>
      <last-name>Franklin</last-name>
    </author>
  </book>
  <book genre="novel">
    <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">
    <title>The Gorgias</title>
    <author>
      <name>Plato</name>
    </author>
    <price>9.99</price>
  </book>
</bookstore>

books.xsd

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns="urn:bookstore-schema"
    elementFormDefault="qualified"
    targetNamespace="urn:bookstore-schema">

 <xsd:element name="bookstore" type="bookstoreType"/>

 <xsd:complexType name="bookstoreType">
  <xsd:sequence maxOccurs="unbounded">
   <xsd:element name="book"  type="bookType"/>
  </xsd:sequence>
 </xsd:complexType>

 <xsd:complexType name="bookType">
  <xsd:sequence>
   <xsd:element name="title" type="xsd:string"/>
   <xsd:element name="author" type="authorName"/>
   <xsd:element name="price"  type="xsd:decimal"/>
  </xsd:sequence>
  <xsd:attribute name="genre" type="xsd:string"/>
 </xsd:complexType>

 <xsd:complexType name="authorName">
  <xsd:sequence>
   <xsd:element name="first-name"  type="xsd:string"/>
   <xsd:element name="last-name" type="xsd:string"/>
  </xsd:sequence>
 </xsd:complexType>

</xsd:schema>

Output

Validation Error: The element 'book' in namespace 'urn:bookstore-schema' has invalid child element 'author' in namespace 'urn:bookstore-schema'. Expected 'title' in namespace 'urn:bookstore-schema'.

Validation Error: The element 'author' in namespace 'urn:bookstore-schema' has invalid child element 'name' in namespace 'urn:bookstore-schema'. Expected 'first-name' in namespace 'urn:bookstore-schema'.

See Also

Concepts

Reading XML with the XmlReader

Other Resources

Validating XML Data with XmlReader