Exam Essentials

Know how to use XSD schemas with a DataSet. Understand that if no schema is provided, the DataSet can construct one based on the data that is loaded. If a schema is explicitly provided, then you have the choice of either restricting the DataSet to loading only data that matches the schema, or adjusting the schema to accommodate new data. Understand how to call the GetSchema method to retrieve the schema that has been generated by the DataSet.

Knowhow to access data in XML files. XML data can be loaded directly into a DataSet with the ReadXml method. The .NET Framework also has other classes that can access XML data, such as the XmlReader, XmlDocument, and XmlDataDocument.

Understand how to use the XmlReader and XmlWriter classes for XML input and output operations. The XmlReader and its three derived classes (XmlTextReader, XmlNodeReader, and XmlValidatingReader) provide forward-only, read-only access to XML data. The XmlReader classes parse an XML document and enable you to read data values sequentially. The XmlTextWriter enables you to create XML output by specifying each item (element, attribute, or text) that should be included, in sequential order, in the output.

Understand how to load XML data into an XML DOM document. The DOM XmlDocument enables you to access the entire XML tree structure in memory. The XML DOM has properties and methods that provide programmatic access to navigate the tree structure, to read and change data values, to create or remove XML nodes, and to change the XML document structure.

Understand how to use XPath expressions to query your XML files to locate specific nodes or sets of nodes. XPath expressions can locate nodes based on their position in a document tree structure, or based on selection criteria that evaluates data values, or a combination of both.

Understand when validating XML data against a schema is important and how to use an XmlValidatingReader to parse a document. Validation can be done with in-line schemas or by using external schema files. Understand the difference between a parsing error (which occurs because of an error in the basic rules of XML markup) and a validation error (which occurs when the data in an XML data file does not match the tag and attribute names, parent/child relationship, element sequence, data types, required/optional settings, or other formatting that can be specified by using XSD schema).

Understand how XSLT can be used to transform XML data from one format to another. XSLT can be used to create HTML-formatted output from XML data. XSLT can also be used when exchanging data with other applications that require variations in the XML format (such as changing a tag name or changing the order of elements) while maintaining data values. XSLT can also be used to create any other text-based output formats that your applications might require.

Understand how to use special SQL syntax to retrieve XML data from SQL Server 2000. The FOR XML clause can be added to standard queries to output XML data. The AUTO, RAW, EXPLICIT, and ELEMENTS modifiers can be used to change the output format. When executing a FOR XML query against SQL Server 2000, use an ADO.NET SqlCommand with the ExecuteXmlReader method to populate an XmlReader with the results from the query.

Understand the features that are available for submitting data to SQL Server 2000 in XML format. These include using an OPENXML clause in a SQL INSERT, UPDATE, or DELETE query.