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XmlSchemaUnique Class

Represents the unique element from XML Schema as specified by the . This class can be used to identify a unique constraint among a set of elements.

Namespace:  System.Xml.Schema
Assembly:  System.Xml (in System.Xml.dll)

'Declaration
Public Class XmlSchemaUnique _
	Inherits XmlSchemaIdentityConstraint

The XmlSchemaUnique type exposes the following members.

  NameDescription
Public methodSupported by the XNA FrameworkXmlSchemaUniqueInitializes a new instance of the XmlSchemaUnique class.
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  NameDescription
Public propertySupported by the XNA FrameworkAnnotationGets or sets the annotation property. (Inherited from XmlSchemaAnnotated.)
Public propertySupported by the XNA FrameworkFieldsGets the collection of fields that apply as children for the XML Path Language (XPath) expression selector. (Inherited from XmlSchemaIdentityConstraint.)
Public propertySupported by the XNA FrameworkIdGets or sets the string id. (Inherited from XmlSchemaAnnotated.)
Public propertySupported by the XNA FrameworkLineNumberGets or sets the line number in the file to which the schema element refers. (Inherited from XmlSchemaObject.)
Public propertySupported by the XNA FrameworkLinePositionGets or sets the line position in the file to which the schema element refers. (Inherited from XmlSchemaObject.)
Public propertySupported by the XNA FrameworkNameGets or sets the name of the identity constraint. (Inherited from XmlSchemaIdentityConstraint.)
Public propertySupported by the XNA FrameworkNamespacesGets or sets the XmlSerializerNamespaces to use with this schema object. (Inherited from XmlSchemaObject.)
Public propertySupported by the XNA FrameworkParentGets or sets the parent of this XmlSchemaObject. (Inherited from XmlSchemaObject.)
Public propertySupported by the XNA FrameworkQualifiedNameGets the qualified name of the identity constraint, which holds the post-compilation value of the QualifiedName property. (Inherited from XmlSchemaIdentityConstraint.)
Public propertySupported by the XNA FrameworkSelectorGets or sets the XPath expression selector element. (Inherited from XmlSchemaIdentityConstraint.)
Public propertySupported by the XNA FrameworkSourceUriGets or sets the source location for the file that loaded the schema. (Inherited from XmlSchemaObject.)
Public propertySupported by the XNA FrameworkUnhandledAttributesGets or sets the qualified attributes that do not belong to the current schema's target namespace. (Inherited from XmlSchemaAnnotated.)
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  NameDescription
Public methodSupported by the XNA FrameworkEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by the XNA FrameworkFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by the XNA FrameworkMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by the XNA FrameworkToStringReturns a string that represents the current object. (Inherited from Object.)
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Specifies that an attribute or element value (or a combination of attribute or element values) must be unique within the specified scope. The constraint name must be unique within a schema.

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>


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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