Type: System.Xml.Schema.XmlSchemaUnique

System.Xml.Schema.XmlSchemaUnique Class

Assembly: System.Xml.dll
Namespace: System.Xml.Schema

Summary: Identifies a unique constraint among a set of elements. Represents the World Wide Web Consortium (W3C) unique element.

C# Syntax:


        public class XmlSchemaUnique : XmlSchemaIdentityConstraint

Remarks

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.

Example

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);
   
        schema.Compile(new ValidationEventHandler(ValidationCallbackOne));
 	XmlNamespaceManager nsmgr = new XmlNamespaceManager(new NameTable());
        nsmgr.AddNamespace("xs", "http://www.w3.org/2001/XMLSchema");
        schema.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>

See also:

System.Xml.Schema Namespace

System.Xml.Schema.XmlSchemaUnique Member List:

Public Constructors

ctor #1

Default constructor. This constructor is called by derived class constructors to initialize state in this type.

Public Properties

Annotation (inherited from System.Xml.Schema.XmlSchemaAnnotated)	Read-write See base class member description: System.Xml.Schema.XmlSchemaAnnotated.Annotation Gets or sets the annotation property.
Fields (inherited from System.Xml.Schema.XmlSchemaIdentityConstraint)	Read-only See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.Fields Gets the collection of fields that apply as children for the XML Path Language (XPath) expression selector.
Id (inherited from System.Xml.Schema.XmlSchemaAnnotated)	Read-write See base class member description: System.Xml.Schema.XmlSchemaAnnotated.Id Gets or sets the string id.
LineNumber (inherited from System.Xml.Schema.XmlSchemaObject)	Read-write See base class member description: System.Xml.Schema.XmlSchemaObject.LineNumber Gets or sets the line number in the file to which the schema element refers.
LinePosition (inherited from System.Xml.Schema.XmlSchemaObject)	Read-write See base class member description: System.Xml.Schema.XmlSchemaObject.LinePosition Gets or sets the line position in the file to which the schema element refers.
Name (inherited from System.Xml.Schema.XmlSchemaIdentityConstraint)	Read-write See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.Name Gets or sets the name of the identity constraint.
Namespaces (inherited from System.Xml.Schema.XmlSchemaObject)	Read-write See base class member description: System.Xml.Schema.XmlSchemaObject.Namespaces
QualifiedName (inherited from System.Xml.Schema.XmlSchemaIdentityConstraint)	Read-only See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.QualifiedName Gets the qualified name of the identity constraint which holds the post-compilation value of the QualifiedName property.
Selector (inherited from System.Xml.Schema.XmlSchemaIdentityConstraint)	Read-write See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.Selector Gets or sets the XML Path Language (XPath) expression selector element.
SourceUri (inherited from System.Xml.Schema.XmlSchemaObject)	Read-write See base class member description: System.Xml.Schema.XmlSchemaObject.SourceUri Gets or sets the source location for the file that loaded the schema.
UnhandledAttributes (inherited from System.Xml.Schema.XmlSchemaAnnotated)	Read-write See base class member description: System.Xml.Schema.XmlSchemaAnnotated.UnhandledAttributes Gets or sets the qualified attributes that do not belong to the schema target namespace.

Public Methods

Equals (inherited from System.Object)	See base class member description: System.Object.Equals Derived from System.Object, the primary base class for all objects.
GetHashCode (inherited from System.Object)	See base class member description: System.Object.GetHashCode Derived from System.Object, the primary base class for all objects.
GetType (inherited from System.Object)	See base class member description: System.Object.GetType Derived from System.Object, the primary base class for all objects.
ToString (inherited from System.Object)	See base class member description: System.Object.ToString Derived from System.Object, the primary base class for all objects.

Protected Methods

Finalize (inherited from System.Object)	See base class member description: System.Object.Finalize Derived from System.Object, the primary base class for all objects.
MemberwiseClone (inherited from System.Object)	See base class member description: System.Object.MemberwiseClone Derived from System.Object, the primary base class for all objects.

Hierarchy:

System.Object

System.Xml.Schema.XmlSchemaObject

System.Xml.Schema.XmlSchemaAnnotated

System.Xml.Schema.XmlSchemaIdentityConstraint

System.Xml.Schema.XmlSchemaUnique

System.Xml.Schema.XmlSchemaUnique Member Details

ctor #1

Summary:: Default constructor. This constructor is called by derived class constructors to initialize state in this type.

C# Syntax:


            public XmlSchemaUnique();

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Property: Annotation (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaAnnotated.Annotation

Summary: Gets or sets the annotation property.

C# Syntax:


            public XmlSchemaAnnotation Annotation {get; set;}

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Property: Fields (read-only)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.Fields

Summary: Gets the collection of fields that apply as children for the XML Path Language (XPath) expression selector.

C# Syntax:


            public XmlSchemaObjectCollection Fields {get;}

Remarks

The collection of fields that apply as children. Each field in the collection specifies the node set under the context element that the identity constraint applies to.

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Property: Id (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaAnnotated.Id

Summary: Gets or sets the string id.

C# Syntax:


            public string Id {get; set;}

Remarks

The id value must be of type ID and be unique within the document containing this element.

Optional.

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Property: LineNumber (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaObject.LineNumber

Summary: Gets or sets the line number in the file to which the schema element refers.

C# Syntax:


            public int LineNumber {get; set;}

Remarks

LineNumber is used to store the line number when a schema is read from a file. This is reported through XmlSchemaException for error handling.

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Property: LinePosition (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaObject.LinePosition

Summary: Gets or sets the line position in the file to which the schema element refers.

C# Syntax:


            public int LinePosition {get; set;}

Remarks

This is used to store the line position when a schema is read from a file. This is reported through XmlSchemaException for error handling.

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Property: Name (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.Name

Summary: Gets or sets the name of the identity constraint.

C# Syntax:


            public string Name {get; set;}

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Property: Namespaces (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaObject.Namespaces

C# Syntax:


            public XmlSerializerNamespaces Namespaces {get; set;}

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Property: QualifiedName (read-only)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.QualifiedName

Summary: Gets the qualified name of the identity constraint which holds the post-compilation value of the QualifiedName property.

C# Syntax:


            public XmlQualifiedName QualifiedName {get;}

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Property: Selector (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaIdentityConstraint.Selector

Summary: Gets or sets the XML Path Language (XPath) expression selector element.

C# Syntax:


            public XmlSchemaXPath Selector {get; set;}

Remarks

An XPath expression that is relative to the element being declared. This expression identifies the node set under the context element that the identity constraint applies to.

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Property: SourceUri (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaObject.SourceUri

Summary: Gets or sets the source location for the file that loaded the schema.

C# Syntax:


            public string SourceUri {get; set;}

Remarks

Provides information for exception handling.

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Property: UnhandledAttributes (read-write)

Inherited
See base class member description: System.Xml.Schema.XmlSchemaAnnotated.UnhandledAttributes

Summary: Gets or sets the qualified attributes that do not belong to the schema target namespace.

C# Syntax:


            public XmlAttribute[] UnhandledAttributes {get; set;}

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Method: Equals(
object obj
)

Inherited
See base class member description: System.Object.Equals

C# Syntax:


            public virtual bool Equals(
   object obj
);