Article ID: 317903
Article Last Modified on 9/4/2003
APPLIES TO
- Microsoft .NET Framework 1.0
- Microsoft .NET Framework 1.1
This article was previously published under Q317903
For a Microsoft Visual C# .NET version of this article, see 318502.
IN THIS TASK
SUMMARY
This step-by-step article shows how to modify an existing XML schema.
The System.Xml.Schema namespace contains the XML classes that provide standards-based support for XML schema definition language (XSD) schemas.
The XmlSchema class contains the definition of a schema. All XSD elements are children of the schema element; this represents the World Wide Web Consortium (W3C) schema element. You can use these classes to generate new XML schemas or modify existing ones.
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Requirements
The following list outlines the recommended hardware, software, network infrastructure, and service packs that are required:
- Microsoft Visual Studio .NET installed on a compatible Microsoft Windows operating system
This article assumes that you are familiar with the following topics:
- Visual Basic .NET language
- XML standards
- XSD schemas
Create an XML Schema File
Paste the following code in a text file, and then save the file as C:\Book.xsd:
<xs:schema xmlns="urn:bookstore-schema" targetNamespace="urn:bookstore-schema" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="book" type="booktype"/> <xs:complexType name="booktype"> <xs:sequence> <xs:element name="author" type="xs:string"/> <xs:element name="price" type="xs:decimal" /> </xs:sequence> </xs:complexType> </xs:schema>
- Modify the author of the element name.
- Set the minOccurs and maxOccurs properties.
- Modify the data type of the element price.
- Add a new element publisher.
Create a Visual Basic .NET Application to Modify the Schema
To add a new publisher child element to the book element of the schema, follow these steps:
- Create a new Visual Basic .NET Console application project.
Replace the code in Module1.vb with the following:
Imports System.Xml Imports System.Xml.Schema Imports System.IO Module Module1 Sub Main() Dim xsd As String = "c:\book.xsd" Dim fs As FileStream Dim schema As XmlSchema Try fs = New FileStream(xsd, FileMode.Open) schema = XmlSchema.Read(fs, New ValidationEventHandler(AddressOf ShowCompileError)) schema.Compile(AddressOf ShowCompileError) 'Create a SchemaObjectTable with the elements of the schema. Dim schematable As XmlSchemaObjectTable schematable = schema.Elements Dim qname As New XmlQualifiedName("book", "urn:bookstore-schema") Dim bookelement As New XmlSchemaElement() Dim complexelement As New XmlSchemaComplexType() If schematable.Contains(qname) Then bookelement = CType(schematable.Item(qname), XmlSchemaElement) Dim simpletype As XmlSchemaSimpleType If (bookelement.SchemaTypeName.ToString = "urn:bookstore-schema:booktype") Then complexelement = schema.SchemaTypes.Item(bookelement.SchemaTypeName) Dim seqelement As New XmlSchemaSequence() seqelement = complexelement.Particle 'Modify author element to show maxOccurs and minOccurs. Dim eleauthor As New XmlSchemaElement() eleauthor = seqelement.Items(0) 'Modify the author element name. eleauthor.Name = "authorname" 'Add min and max. eleauthor.MaxOccurs = 1 eleauthor.MinOccurs = 1 Dim eleprice As New XmlSchemaElement() eleprice = seqelement.Items(1) 'Modify the type of price element. eleprice.SchemaTypeName = New XmlQualifiedName("decimal", "http://www.w3.org/2001/XMLSchema") 'Create a new element and add to the schema Dim Newelement As New XmlSchemaElement() Newelement.Name = "Publisher" Newelement.SchemaTypeName = New XmlQualifiedName("string", "http://www.w3.org/2001/XMLSchema") seqelement.Items.Add(Newelement) End If End If 'Display the schema in the Output window. schema.Write(Console.Out) Console.Read() 'Save to the hard disk. Dim Newschema As New StreamWriter("c:\Newbooks.xsd", False) schema.Write(Newschema) Catch exp As XmlSchemaException Console.WriteLine(exp.Message) Catch exp As XmlException Console.WriteLine(exp.Message) Catch exp As Exception Console.WriteLine(exp.Message) Finally Console.Read() End Try End Sub Public Sub ShowCompileError(ByVal sender As Object, ByVal e As ValidationEventArgs) Console.WriteLine("Validation Error: {0}", e.Message) End Sub End Module
XmlSchemaObjectTable is a collection class that provides read-only helpers for XmlSchemaObject objects. This class is used to provide the collections for contained elements that are in the schema as collections that are accessed from the XmlSchema class; for example, Attributes, AttributeGroups, and Elements.
Because you are trying to add a child element publisher to a book element, add the new element to the XmlSchemaSequence. The XmlSchemaSequence class represents the World Wide Web Consortium SEQUENCE (compositor) element.- Press F5 to build and run the application.
The new schema that includes the publisher element appears in the Console output area. Also, the XSD file named Newbook.xsd is created in the C:\ folder.
REFERENCES
For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:
313826 INFO: Roadmap for XML Schemas in the .NET Framework
313651 INFO: Roadmap for XML in the .NET Framework
For additional information, see the following MSDN Web sites:
Additional query words: EditXmlSchema ModifyXmlSchema
Keywords: kbhowtomaster kbinfo KB317903