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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)

'Declaration
Public Class XmlSchemaKeyref _
	Inherits XmlSchemaIdentityConstraint
'Usage
Dim instance As XmlSchemaKeyref

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.

Imports System
Imports System.Collections
Imports System.IO
Imports System.Xml
Imports System.Xml.Xsl
Imports System.Xml.Schema

Public Class XmlSchemaObjectGenerator

   Private Shared Sub ValidationCallback(sender As Object, args As ValidationEventArgs)

      If args.Severity = XmlSeverityType.Warning Then
         Console.Write("WARNING: ")
      Else 
         If args.Severity = XmlSeverityType.Error Then
            Console.Write("ERROR: ")
         End If  
      End If
      Console.WriteLine(args.Message)
   End Sub 'ValidationCallback



   Public Shared Sub Main()


      Dim tr As New XmlTextReader("empty.xsd")
      Dim schema As XmlSchema = XmlSchema.Read(tr, New ValidationEventHandler(AddressOf ValidationCallback))

      schema.ElementFormDefault = XmlSchemaForm.Qualified

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

      If (True) Then 

         Dim element As New XmlSchemaElement()
         element.Name = "purchaseReport" 

         Dim element_complexType As New XmlSchemaComplexType()

         Dim element_complexType_sequence As New XmlSchemaSequence()

         If (True) Then 

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

            If (True) Then 

               Dim element_complexType_sequence_element_keyref As 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" 

               If (True) Then 
                  Dim field As New XmlSchemaXPath()

                  field.XPath = "@number"
                  element_complexType_sequence_element_keyref.Fields.Add(field)
               End If
               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)
            End If
            element_complexType_sequence.Items.Add(element_complexType_sequence_element)
         End If
         element_complexType.Particle = element_complexType_sequence

         If (True) Then 

            Dim element_complexType_attribute As 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)
         End If
         element.SchemaType = element_complexType

         If (True) Then 

            Dim element_key As New XmlSchemaKey()
            element_key.Name = "pNumKey"
            element_key.Selector = New XmlSchemaXPath()
            element_key.Selector.XPath = "r:parts/r:part" 

            If (True) Then 
               Dim field As New XmlSchemaXPath()

               field.XPath = "@number"
               element_key.Fields.Add(field)
            End If
            element.Constraints.Add(element_key)
         End If

         schema.Items.Add(element)
      End If

      schema.Write(Console.Out)
   End Sub 'Main 
End Class 'XmlSchemaObjectGenerator 

' 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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