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XmlSchemaSimpleTypeUnion Class

Represents the union element for simple types from XML Schema as specified by the World Wide Web Consortium (W3C). A union datatype can be used to specify the content of a simpleType. The value of the simpleType element must be any one of a set of alternative datatypes specified in the union. Union types are always derived types and must comprise at least two alternative datatypes.

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

public class XmlSchemaSimpleTypeUnion : XmlSchemaSimpleTypeContent

A union type enables an element or attribute value to be one or more instances of one type drawn from the union of multiple atomic and list types.

The following example shows the use of XmlSchemaSimpleTypeUnion class.

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

class XMLSchemaExamples
    public static void Main()

        XmlSchema schema = new XmlSchema();

        //<xs:simpleType name="StringOrIntType">
        XmlSchemaSimpleType StringOrIntType = new XmlSchemaSimpleType();
        StringOrIntType.Name = "StringOrIntType";

        // <xs:union>
        XmlSchemaSimpleTypeUnion union = new XmlSchemaSimpleTypeUnion();
        StringOrIntType.Content = union;

        // <xs:simpleType>
        XmlSchemaSimpleType simpleType1 = new XmlSchemaSimpleType();

        // <xs:restriction base="xs:string"/>
        XmlSchemaSimpleTypeRestriction restriction1 = new XmlSchemaSimpleTypeRestriction();
        restriction1.BaseTypeName = new XmlQualifiedName("string", "");
        simpleType1.Content = restriction1;

        // <xs:simpleType>
        XmlSchemaSimpleType simpleType2 = new XmlSchemaSimpleType();

        // <xs:restriction base="xs:int"/>
        XmlSchemaSimpleTypeRestriction restriction2 = new XmlSchemaSimpleTypeRestriction();
        restriction2.BaseTypeName = new XmlQualifiedName("int", "");
        simpleType2.Content = restriction2;

        // <xs:element name="size" type="StringOrIntType"/>
        XmlSchemaElement elementSize = new XmlSchemaElement();
        elementSize.Name = "size";
        elementSize.SchemaTypeName = new XmlQualifiedName("StringOrIntType");

        XmlSchemaSet schemaSet = new XmlSchemaSet();
        schemaSet.ValidationEventHandler += new ValidationEventHandler(ValidationCallbackOne);

        XmlSchema compiledSchema = null;

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

        XmlNamespaceManager nsmgr = new XmlNamespaceManager(new NameTable());
        nsmgr.AddNamespace("xs", "");
        compiledSchema.Write(Console.Out, nsmgr);

    public static void ValidationCallbackOne(object sender, ValidationEventArgs args)

The following XML file is generated for this code example.

<?xml version="1.0" encoding="IBM437"?>
<xs:schema xmlns:xs="">

    <xs:simpleType name="StringOrIntType">
                <xs:restriction base="xs:string"/>

                <xs:restriction base="xs:int"/>

    <xs:element name="size" type="StringOrIntType"/>

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