Validation Using a DTD with XmlReader
Document type definition (DTD) validation is implemented using the validity constraints defined in the World Wide Web Consortium (W3C) Extensible Markup Language (XML) 1.0 Recommendation. DTDs use a formal grammar to describe the structure and syntax of compliant XML documents; they specify content and values allowed for the XML document.
To perform validation against a DTD, the XmlReader uses the DTD defined in the DOCTYPE declaration of an XML document. The DOCTYPE declaration can either point to an inline DTD or can be a reference to an external DTD file.
Set the XmlReaderSettings.ProhibitDtd property to false.
Set the XmlReaderSettings.ValidationType property to ValidationType.DTD.
If the DTD is an external file stored on a network resource that requires authentication, pass an XmlResolver object with the necessary credentials to the Create method.
Example
The following example validates an XML file using a DTD file.
Imports System
Imports System.Xml
Imports System.Xml.Schema
Imports System.IO
public class Sample
public shared sub Main()
' Set the validation settings.
Dim settings as XmlReaderSettings = new XmlReaderSettings()
settings.ProhibitDtd = false
settings.ValidationType = ValidationType.DTD
AddHandler settings.ValidationEventHandler, AddressOf ValidationCallBack
' Create the XmlReader object.
Dim reader as XmlReader = XmlReader.Create("itemDTD.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() {
// Set the validation settings.
XmlReaderSettings settings = new XmlReaderSettings();
settings.ProhibitDtd = false;
settings.ValidationType = ValidationType.DTD;
settings.ValidationEventHandler += new ValidationEventHandler (ValidationCallBack);
// Create the XmlReader object.
XmlReader reader = XmlReader.Create("itemDTD.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()
{
// Set the validation settings.
XmlReaderSettings^ settings = gcnew XmlReaderSettings;
settings->ProhibitDtd = false;
settings->ValidationType = ValidationType::DTD;
settings->ValidationEventHandler += gcnew ValidationEventHandler( ValidationCallBack );
// Create the XmlReader object.
XmlReader^ reader = XmlReader::Create( L"itemDTD.xml", settings );
// Parse the file.
while ( reader->Read() )
;
return 1;
}
// Set the validation settings.
XmlReaderSettings* settings = new XmlReaderSettings();
settings->DtdValidate = true;
settings->ValidationEventHandler += new ValidationEventHandler (ValidationCallBack);
// Create the XmlReader object.
XmlReader* reader = XmlReader::Create(S"itemDTD.xml", settings);
// Parse the file.
while (reader->Read());
Input
The example uses the itemDTD.xml file as input.
<!--XML file using a DTD-->
<!DOCTYPE store [
<!ELEMENT store (item)*>
<!ELEMENT item (name,dept,price)>
<!ATTLIST item type CDATA #REQUIRED>
<!ELEMENT name (#PCDATA)>
<!ELEMENT price (#PCDATA)>]>
<store>
<item type="supplies" ISBN="2-3631-4">
<name>paint</name>
<price>16.95</price>
</item>
</store>
See Also
Concepts
Reading XML with the XmlReader