MIS 426

1
MIS 426

• Chapter 13, Using XML with DataSets

2
Overview of XML Classes

• The .Net framework contains a rich set of classes
  for working with XML
• This will only provide an overview of a few of
  those classes

3
Objectives

• In this chapter you should learn how to
• Use XML with DataSets
• Transform XML with XSL Stylesheets
• Use the ASP.NET Xml Control
• Use the XslTransform Class
• Use Strongly Typed DataSets (yea!)

4
Overview of XML Classes

• The main classes are
• XmlTextReader This class is for fast forward
  only access to the raw data in an XML file (read
  XML from a file)
• XmlTextWriter This class is a fast forward
  only method to write data to an XML file (write
  XML to a file)
• XmlDocument This class represents XML using the
  Document Object Model (DOM) to either navigate or
  edit the nodes in the XML document in a dataset
• XmlDataDocument This class allows you to
  represent both XML and relational data structures
  in the DOM. This can be used with a DataSet to
  provide both relational and non-relational
  (tree)views of the same data

5
Overview of XML Classes

• XmlNodeReader This class provides fast forward
  only access to data represented by the
  XmlDocument or XmlDataDocument class
• XslTransform This class enables you to
  transform an XML document into an HTML document
  with XSL stylesheets

6
Using XML with DataSets

• A DataSet can represent XML data in two ways
• You can load XML data directly into a
  DataSetdsMenu.ReadXml( MapPath( "ReadMenu.xml" )
  )
• View an Example
• You can build an XmlDataDocument class from an
  existing data set
• You can bind XML data to any of the standard
  ASP.NET controls that have a DataSource Property

7
Using a Schema with ReadXML so you can strongly
type the data (not all treated as strings)

• You can specify a schema with an XML file in two
  ways
• You can include the schema in the same document
  as the XML filedsMenu.ReadXml(MapPath(
  "ReadSchemaData.xml" ))
• View an Example
• You can read the schema separately by using the
  ReadXmlSchema Method
• View an Example

8
Writing an XML Document from a DS

• You can retrieve a string representation of the
  XML data with the GetXML() Method.
• This allows you to output an XML representation
  of a DataSet to the browserstrXmlData
  dstTitles.GetXml()Response.Write( "ltpregt"
  Server.HtmlEncode( strXmlData ) "lt/pregt" )
• View an Example
• You can also use this to write an XML
  representation to a file on the hard
  drivedstTitles.WriteXml( "c\myXml.xml" )
• View an Example

9
Using XMLDataDocs with Datasets

• Sometimes it makes more sense to represent XML
  data as nodes on a tree as opposed to relational
  (tabular) data
• View an example of relation data that would be
  better displayed as nodes
• XMLDataDocuments represents data as nodes on a
  tree. You create a new XMLDataDocument by using
  a Dataset in the XML DataDocuments constructor
• objDataDocument New XmlDataDocument(
  dstRecipes) objRecipes objDataDocument.GetElemen
  tsByTagName( "Ingredient" )
• The GetElementsByTagName method retrievesa list
  of nodes that have the tagname identified View
  the data displayed as nodes

10
Transforming XML with XSL Stylesheets

• One common use for XSL stylesheets is to convert
  XML into nicely formatted HTML
• Another use for XSL is for data format conversion
• To accomplish this you can use the ASP.NET Xml
  Control or you can use the XSLTransform Class

11
Using the ASP.NET Xml Control

• You can use this control to simply display raw
  XML or you can use it with a stylesheet to format
  the XML
• The XML control supports the following
  properties
• DocumentSource The path to the XML file
• TransformSource The path to the XSL file
• Document A preloaded XML document
• Transform a preloaded XSL stylesheet
• View an Example

12
Using the XslTransform Class

• The XslTransform class enables you to work with
  the XSL transform without displaying the results
• You can use the XslTransform class to transform
  an XML document then save it to the file system
• View an Example

13
Using Strongly Typed DataSets

• You can access data in a DataSet by working with
  collections (such as tables, ros, columns) using
  string literals
• or you can access the data by using strongly
  typed methods and properties specified by an XML
  schema
• With strongly typed DataSets you can refer to
  tables and columns as named properties of the
  dataset (EX label1.text dsEmployees.Firstname
  (0))

14
Using Strongly Typed DataSets

• When you create a typed DataSet you create a new
  class that represents the DataSet
• To create a strongly typed DataSet you must
• Create an XML schema that represents the
  structure of the DataSet
• Use the XML schema with the Xsd.exe command line
  tool to generate the source code for a class that
  represents the DataSet
• Compile the source code for the class and copy
  the compiled class into your applications /bin
  directory

15
To Create a Strongly Typed DataSet

• View the XML Schema for the Titles table in the
  Pubs database
• View the code and get the file
• Copy the resulting file and save it
• Open the command line and execute the following
  code Xsd.exe /d /lvb FileName.xsd
• Now compile the this file vbc /tlibrary
  /rSystem.dll,System.Data.dll,System.Xml.dll
  TitlesDS.vb
• Now copy this file to the /bin directory
• View an example of how to utilize this strongly
  typed DataSet