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XmlSchemaKeyref Class

This class represents the keyref element from XMLSchema as specified by the World Wide Web Consortium (W3C).

Namespace:  System.Xml.Schema
Assembly:  System.Xml (in System.Xml.dll)
public class XmlSchemaKeyref : XmlSchemaIdentityConstraint

Specifies that an attribute or element value (or set of values) has a correspondence with those of the specified key or unique element. The constraint name must be unique within a schema.

The following example creates a key element.

using System;
using System.Collections;
using System.IO;
using System.Xml;
using System.Xml.Xsl;
using System.Xml.Schema;

public class XmlSchemaObjectGenerator {



    private static void ValidationCallback(object sender, ValidationEventArgs args ){

	if(args.Severity == XmlSeverityType.Warning)
	    Console.Write("WARNING: ");
	else if(args.Severity == XmlSeverityType.Error)
	    Console.Write("ERROR: ");

	Console.WriteLine(args.Message);
    }
	                  

    public static void Main() {

		 
	  XmlTextReader tr = new XmlTextReader("empty.xsd");
        XmlSchema schema = XmlSchema.Read(tr, new ValidationEventHandler(ValidationCallback));

            schema.ElementFormDefault = XmlSchemaForm.Qualified;

            schema.TargetNamespace = "http://www.example.com/Report";

            {

        XmlSchemaElement element = new XmlSchemaElement();
        element.Name = "purchaseReport";

        XmlSchemaComplexType element_complexType = new XmlSchemaComplexType();

        XmlSchemaSequence element_complexType_sequence = new XmlSchemaSequence();

            {

        XmlSchemaElement element_complexType_sequence_element = new XmlSchemaElement();
        element_complexType_sequence_element.Name = "region";
        element_complexType_sequence_element.SchemaTypeName = 
				new XmlQualifiedName("string", "http://www.w3.org/2001/XMLSchema")
			;

            {

        XmlSchemaKeyref element_complexType_sequence_element_keyref = new XmlSchemaKeyref();
        element_complexType_sequence_element_keyref.Name = "dummy2";
        element_complexType_sequence_element_keyref.Selector = new XmlSchemaXPath();
			element_complexType_sequence_element_keyref.Selector.XPath = "r:zip/r:part";

            {
				XmlSchemaXPath field = new XmlSchemaXPath();
				
				field.XPath = "@number";
                element_complexType_sequence_element_keyref.Fields.Add(field);
            }
        element_complexType_sequence_element_keyref.Refer =  
				new XmlQualifiedName("pNumKey", "http://www.example.com/Report")
			;
        element_complexType_sequence_element.Constraints.Add(element_complexType_sequence_element_keyref);
            }
        element_complexType_sequence.Items.Add(element_complexType_sequence_element);
            }
        element_complexType.Particle = element_complexType_sequence;

            {

        XmlSchemaAttribute element_complexType_attribute = new XmlSchemaAttribute();
        element_complexType_attribute.Name = "periodEnding";
        element_complexType_attribute.SchemaTypeName = 
				new XmlQualifiedName("date", "http://www.w3.org/2001/XMLSchema")
			;
        element_complexType.Attributes.Add(element_complexType_attribute);
            }
        element.SchemaType = element_complexType;

            {

        XmlSchemaKey element_key = new XmlSchemaKey();
        element_key.Name = "pNumKey";
        element_key.Selector = new XmlSchemaXPath();
			element_key.Selector.XPath = "r:parts/r:part";

            {
				XmlSchemaXPath field = new XmlSchemaXPath();
				
				field.XPath = "@number";
                element_key.Fields.Add(field);
            }
        element.Constraints.Add(element_key);
            }

                schema.Items.Add(element);
            }

	    schema.Write(Console.Out);



    }/* Main() */ 

} 
//XmlSchemaObjectGenerator
#using <mscorlib.dll>
#using <System.Xml.dll>
using namespace System;
using namespace System::Collections;
using namespace System::IO;
using namespace System::Xml;
using namespace System::Xml::Xsl;
using namespace System::Xml::Schema;

__gc public class XmlSchemaObjectGenerator
{
public:
   static void ValidationCallback(Object* /*sender*/, ValidationEventArgs * args)
   {
      if (args -> Severity == XmlSeverityType::Warning)
         Console::Write(S"WARNING: ");
      else if (args -> Severity == XmlSeverityType::Error)
         Console::Write(S"ERROR: ");
      Console::WriteLine(args -> Message);
   }
}; // XmlSchemaObjectGenerator

int main()
{
   XmlTextReader* tr = new XmlTextReader(S"empty.xsd");
   XmlSchema * schema = XmlSchema::Read(tr, new ValidationEventHandler(schema, XmlSchemaObjectGenerator::ValidationCallback));

   schema -> ElementFormDefault = XmlSchemaForm::Qualified;

   schema -> TargetNamespace = S"http://www.example.com/Report";
   {
      XmlSchemaElement* element = new XmlSchemaElement();
      element -> Name = S"purchaseReport";

      XmlSchemaComplexType* element_complexType = new XmlSchemaComplexType();

      XmlSchemaSequence* element_complexType_sequence = new XmlSchemaSequence();
      {
         XmlSchemaElement* element_complexType_sequence_element = new XmlSchemaElement();
         element_complexType_sequence_element -> Name = S"region";
         element_complexType_sequence_element -> SchemaTypeName = new XmlQualifiedName(S"String*", S"http://www.w3.org/2001/XMLSchema");
         {
            XmlSchemaKeyref* element_complexType_sequence_element_keyref = new XmlSchemaKeyref();
            element_complexType_sequence_element_keyref -> Name = S"dummy2";
            element_complexType_sequence_element_keyref -> Selector = new XmlSchemaXPath();
            element_complexType_sequence_element_keyref -> Selector -> XPath = S"r:zip/r:part";
            {
               XmlSchemaXPath* field = new XmlSchemaXPath();
               field -> XPath = S"@number";
               element_complexType_sequence_element_keyref -> Fields->Add(field);
            }
            element_complexType_sequence_element_keyref -> Refer = new XmlQualifiedName(S"pNumKey", S"http://www.example.com/Report");
            element_complexType_sequence_element -> Constraints->Add(element_complexType_sequence_element_keyref);
         }
         element_complexType_sequence -> Items->Add(element_complexType_sequence_element);
      }
      element_complexType -> Particle = element_complexType_sequence;
      {
         XmlSchemaAttribute* element_complexType_attribute = new XmlSchemaAttribute();
         element_complexType_attribute -> Name = S"periodEnding";
         element_complexType_attribute -> SchemaTypeName = new XmlQualifiedName(S"date", S"http://www.w3.org/2001/XMLSchema");
         element_complexType -> Attributes->Add(element_complexType_attribute);
      }
      element -> SchemaType = element_complexType;
      {
         XmlSchemaKey* element_key = new XmlSchemaKey();
         element_key -> Name = S"pNumKey";
         element_key -> Selector = new XmlSchemaXPath();
         element_key -> Selector -> XPath = S"r:parts/r:part";
       {
          XmlSchemaXPath* field = new XmlSchemaXPath();
          field -> XPath = S"@number";
          element_key -> Fields->Add(field);
       }
       element -> Constraints->Add(element_key);
      }
      schema -> Items->Add(element);
   }
   schema -> Write(Console::Out);
} // main

The following XML file is generated for the preceding code example.

<?xml version="1.0" encoding="IBM437"?>
<xs:schema xmlns:r="http://www.example.com/Report" elementFormDefault="qualified" targetNamespace="http://www.example.com/Report" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="purchaseReport">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="region" type="xs:string">
          <xs:keyref name="dummy2" refer="r:pNumKey">
            <xs:selector xpath="r:zip/r:part" />
            <xs:field xpath="@number" />
          </xs:keyref>
        </xs:element>
      </xs:sequence>
      <xs:attribute name="periodEnding" type="xs:date" />
    </xs:complexType>
    <xs:key name="pNumKey">
      <xs:selector xpath="r:parts/r:part" />
      <xs:field xpath="@number" />
    </xs:key>
  </xs:element>
</xs:schema>
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0
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