Knowledge Base

HOW TO: Use the AddSort Method of the XPathExpression Object in Visual C# .NET

Article ID: 318542

Article Last Modified on 9/22/2003

APPLIES TO

Microsoft Visual C# .NET 2003 Standard Edition
Microsoft Visual C# .NET 2002 Standard Edition
Microsoft .NET Framework 1.0
Microsoft .NET Framework 1.1

This article was previously published under Q318542

For a Microsoft Visual Basic .NET version of this article, see 317084.

Requirements
Create the Sample XML Document
Create the Sample Visual C# .Net Application
Test the Sample Code

SUMMARY

This step-by-step article demonstrates how to use the AddSort method of the System.Xml.XPath.XPathExpression class to sort the results of an XML Path Language (XPath) query that is based on a specified element or attribute.

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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 are familiar with the following topics:

Visual C# language
XML standards
XPath query language

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Create the Sample XML Document

In Notepad, create a new XML document that contains the following code:

<?xml version='1.0'?>
<Books>
<Book>
  <Title>Advanced XML</Title>
  <Publisher>Lucerne Publishing</Publisher>
</Book>
<Book>
  <Title>Learn XML Today</Title>
  <Publisher>MSPress</Publisher>
</Book>
<Book>
  <Title>XML for Gurus</Title>
  <Publisher>Lucerne Publishing</Publisher>
</Book>
<Book>
  <Title>Developing XML solutions</Title>
  <Publisher>MSPress</Publisher>
</Book>
</Books>

Save the document as Books.xml in the root folder of your hard disk.

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Create the Sample Visual C# .NET Application

Follow these steps to create a new Visual C# .NET Windows Application project:
1. Start Microsoft Visual Studio .NET.
2. On the File menu, point to New, and then click Project.
3. In the New Project dialog box, click Visual C# Projects under Project Types, and then click Windows Application under Templates.
Drag a Button control from the toolbox to Form1.cs.

Double-click the button in Design view. In the Click event procedure, add the following code to create a handler for the Click event of the Button control:

// Construct the XPathDocument by specifying the path to Books.xml.
System.Xml.XPath.XPathDocument xmldoc = new System.Xml.XPath.XPathDocument("c:\\books.xml");

// Create the XPathNavigator.
System.Xml.XPath.XPathNavigator nav = xmldoc.CreateNavigator();

// Compile the XPath query expression to select all the Title elements.
// The Compile method of the XPathNavigator generates an XPathExpression 
// object that encapsulates the compiled query.
System.Xml.XPath.XPathExpression expr  = nav.Compile("/Books/Book/Title");

// Execute the AddSort method of the XPathExpression object to define the 
// Title Element as the sort key.
expr.AddSort(".", System.Xml.XPath.XmlSortOrder.Ascending, System.Xml.XPath.XmlCaseOrder.None, "", System.Xml.XPath.XmlDataType.Text);


// Create the XPathNodeIterator by executing the Select method of the 
// XPathNavigator. Notice that the XPathExpression object is supplied as 
// the query expression parameter.
System.Xml.XPath.XPathNodeIterator iterator  = nav.Select(expr);

System.Diagnostics.Debug.WriteLine("Titles sorted in Ascending order...");
System.Diagnostics.Debug.WriteLine("***********************************");

// Use the iterator to explore the result set that is generated.
while (iterator.MoveNext())
{
   System.Diagnostics.Debug.WriteLine(iterator.Current.Value);
}

Read the inline comments to understand the functionality of the code. Notice the line of code that executes the AddSort method of the XPathExpression object.

public abstract void AddSort(
   object expr,
   XmlSortOrder order,
   XmlCaseOrder caseOrder,
   string lang,
   XmlDataType dataType
);

The following is a description of the parameters in the overload of the AddSort method that are used in this sample:

expr         An expression that represents the sort key. This can be a 
             string or an XPathExpression object. The result of this 
             expression is converted to a string, according to the XPath 
             specification. In an XSLT style sheet, if you use xsl:sort but 
             do not specify a select expression, string(.) is used by 
             default. 

order        A System.Xml.XPath.XmlSortOrder enumeration value that 
             indicates the sort order. 

caseOrder    A System.Xml.XPath.XmlCaseOrder enumeration value that 
             indicates how to sort uppercase and lowercase letters. This is 
             language-dependent if you supply a lang parameter. 

lang         The language to use for comparison. Uses the CultureInfo class 
             that you can pass to the String.Compare method for the 
             language types (for example, "us-en" for U.S. English). If you 
             specify an empty string, the system environment is used to 
             determine the CultureInfo. 

dataType     System.Xml.XPath.XmlDataType enumeration value that indicates 
             sort order for a data type.

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Test the Sample Code

Save the changes to the Visual C# .NET project, and then run the project.

When the form appears, click the button to execute the code. A list of titles appears in the Visual Studio .NET Output window, and the titles are sorted in ascending order:

Titles sorted in Ascending order...
***********************************
Advanced XML
Developing XML solutions
Learn XML Today
XML for Gurus

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REFERENCES

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

313828 INFO: Roadmap for Executing XPath Queries in .NET Applications

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Additional query words: execute XPath queries

Keywords: kbhowtomaster KB318542

Microsoft KB Archive/318542

Contents

HOW TO: Use the AddSort Method of the XPathExpression Object in Visual C# .NET

In This Task

SUMMARY

Requirements

Create the Sample XML Document

Create the Sample Visual C# .NET Application

Test the Sample Code

REFERENCES