XmlSchemaUnique Class
Represents the unique element from XML Schema as specified by the World Wide Web Consortium (W3C). This class can be used to identify a unique constraint among a set of elements.
Assembly: System.Xml (in System.Xml.dll)
The following example shows the use of the XmlSchemaUnique class.
Imports System Imports System.Xml Imports System.Xml.Schema Class XMLSchemaExamples Public Shared Sub Main() Dim schema As New XmlSchema() ' <xs:complexType name="customerOrderType"> Dim customerOrderType As New XmlSchemaComplexType() customerOrderType.Name = "customerOrderType" ' <xs:sequence> Dim sequence1 As New XmlSchemaSequence() ' <xs:element name="item" minOccurs="0" maxOccurs="unbounded"> Dim item As New XmlSchemaElement() item.MinOccurs = 0 item.MaxOccursString = "unbounded" item.Name = "item" ' <xs:complexType> Dim ct1 As New XmlSchemaComplexType() ' <xs:attribute name="itemID" type="xs:string"/> Dim itemID As New XmlSchemaAttribute() itemID.Name = "itemID" itemID.SchemaTypeName = New XmlQualifiedName("string", "http://www.w3.org/2001/XMLSchema") ' </xs:complexType> ct1.Attributes.Add(itemID) ' </xs:element> item.SchemaType = ct1 ' </xs:sequence> sequence1.Items.Add(item) customerOrderType.Particle = sequence1 ' <xs:attribute name="CustomerID" type="xs:string"/> Dim CustomerID As New XmlSchemaAttribute() CustomerID.Name = "CustomerID" CustomerID.SchemaTypeName = New XmlQualifiedName("string", "http://www.w3.org/2001/XMLSchema") customerOrderType.Attributes.Add(CustomerID) ' </xs:complexType> schema.Items.Add(customerOrderType) ' <xs:element name="ordersByCustomer"> Dim ordersByCustomer As New XmlSchemaElement() ordersByCustomer.Name = "ordersByCustomer" ' <xs:complexType> Dim ct2 As New XmlSchemaComplexType() ' <xs:sequence> Dim sequence2 As New XmlSchemaSequence() ' <xs:element name="customerOrders" type="customerOrderType" minOccurs="0" maxOccurs="unbounded" /> Dim customerOrders As New XmlSchemaElement() customerOrders.MinOccurs = 0 customerOrders.MaxOccursString = "unbounded" customerOrders.Name = "customerOrders" customerOrders.SchemaTypeName = New XmlQualifiedName("customerOrderType", "") ' </xs:sequence> sequence2.Items.Add(customerOrders) ' </xs:complexType> ct2.Particle = sequence2 ordersByCustomer.SchemaType = ct2 ' <xs:unique name="oneCustomerOrdersforEachCustomerID"> Dim element_unique As New XmlSchemaUnique() element_unique.Name = "oneCustomerOrdersforEachCustomerID" ' <xs:selector xpath="customerOrders"/> element_unique.Selector = New XmlSchemaXPath() element_unique.Selector.XPath = "customerOrders" ' <xs:field xpath="@customerID"/> Dim field As New XmlSchemaXPath() field.XPath = "@customerID" ' </xs:unique> element_unique.Fields.Add(field) ordersByCustomer.Constraints.Add(element_unique) ' </xs:element> schema.Items.Add(ordersByCustomer) Dim schemaSet As New XmlSchemaSet() AddHandler schemaSet.ValidationEventHandler, AddressOf ValidationCallbackOne schemaSet.Add(schema) schemaSet.Compile() Dim compiledSchema As XmlSchema = Nothing For Each schema1 As XmlSchema In schemaSet.Schemas() compiledSchema = schema1 Next Dim nsmgr As New XmlNamespaceManager(New NameTable()) nsmgr.AddNamespace("xs", "http://www.w3.org/2001/XMLSchema") compiledSchema.Write(Console.Out, nsmgr) End Sub Public Shared Sub ValidationCallbackOne(ByVal sender As Object, ByVal args As ValidationEventArgs) Console.WriteLine(args.Message) End Sub End Class
The following XML file is generated for this code example.
<?xml version="1.0" encoding="IBM437"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:complexType name="customerOrderType"> <xs:sequence> <xs:element name="item" minOccurs="0" maxOccurs="unbounded"> <xs:complexType> <xs:attribute name="itemID" type="xs:string"/> </xs:complexType> </xs:element> </xs:sequence> <xs:attribute name="CustomerID" type="xs:string"/> </xs:complexType> <xs:element name="ordersByCustomer"> <xs:complexType> <xs:sequence> <xs:element name="customerOrders" type="customerOrderType" minOccurs="0" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType> <xs:unique name="oneCustomerOrdersforEachCustomerID"> <xs:selector xpath="customerOrders"/> <xs:field xpath="@customerID"/> </xs:unique> </xs:element> </xs:schema>
System.Xml.Schema.XmlSchemaObject
System.Xml.Schema.XmlSchemaAnnotated
System.Xml.Schema.XmlSchemaIdentityConstraint
System.Xml.Schema.XmlSchemaUnique
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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.