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XmlSchemaUnique Class
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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.

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

public class XmlSchemaUnique : 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 the default hash function. (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.

using System;
using System.Xml;
using System.Xml.Schema;

class XMLSchemaExamples
{
    public static void Main()
    {

        XmlSchema schema = new XmlSchema();

        // <xs:complexType name="customerOrderType">
        XmlSchemaComplexType customerOrderType = new XmlSchemaComplexType();
        customerOrderType.Name = "customerOrderType";

        // <xs:sequence>
        XmlSchemaSequence sequence1 = new XmlSchemaSequence();

        // <xs:element name="item" minOccurs="0" maxOccurs="unbounded">
        XmlSchemaElement item = new XmlSchemaElement();
        item.MinOccurs = 0;
        item.MaxOccursString = "unbounded";
        item.Name = "item";

        // <xs:complexType>
        XmlSchemaComplexType ct1 = new XmlSchemaComplexType();

        // <xs:attribute name="itemID" type="xs:string"/>
        XmlSchemaAttribute itemID = 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"/>
        XmlSchemaAttribute CustomerID = 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">
        XmlSchemaElement ordersByCustomer = new XmlSchemaElement();
        ordersByCustomer.Name = "ordersByCustomer";

        // <xs:complexType>
        XmlSchemaComplexType ct2 = new XmlSchemaComplexType();

        // <xs:sequence>
        XmlSchemaSequence sequence2 = new XmlSchemaSequence();

        // <xs:element name="customerOrders" type="customerOrderType" minOccurs="0" maxOccurs="unbounded" />
        XmlSchemaElement customerOrders = 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">
        XmlSchemaUnique element_unique = new XmlSchemaUnique();
        element_unique.Name = "oneCustomerOrdersforEachCustomerID";

        // <xs:selector xpath="customerOrders"/>
        element_unique.Selector = new XmlSchemaXPath();
        element_unique.Selector.XPath = "customerOrders";

        // <xs:field xpath="@customerID"/>
        XmlSchemaXPath field = new XmlSchemaXPath();
        field.XPath = "@customerID";

        // </xs:unique>
        element_unique.Fields.Add(field);
        ordersByCustomer.Constraints.Add(element_unique);

        // </xs:element>
        schema.Items.Add(ordersByCustomer);

        XmlSchemaSet schemaSet = new XmlSchemaSet();
        schemaSet.ValidationEventHandler += new ValidationEventHandler(ValidationCallbackOne);
        schemaSet.Add(schema);
        schemaSet.Compile();

        XmlSchema compiledSchema = null;

        foreach (XmlSchema schema1 in schemaSet.Schemas())
        {
            compiledSchema = schema1;
        }

        XmlNamespaceManager nsmgr = new XmlNamespaceManager(new NameTable());
        nsmgr.AddNamespace("xs", "http://www.w3.org/2001/XMLSchema");
        compiledSchema.Write(Console.Out, nsmgr);
    }

    public static void ValidationCallbackOne(object sender, ValidationEventArgs args)
    {
        Console.WriteLine(args.Message);
    }
}

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: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

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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