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XPathParser: XPath parser in C# source code.

Build status

Close to one System.Xml uses in the XslCompiledTransform. Currently supports XPath 1.0 grammar.

This implementation uses Builder pattern to separate parsing code from result the parser should produce.

While parsing the source XPath parser calls method in the methods of IXPathBuilder interface provided by caller.

User of this code expected to write his own IXPathBuilder implementation. Source code of this project contains two IXPathBuilder implementations for demo/testing purpose:

  • XPathTreeBuilder - constructs XLinq tree that represents XPath syntax tree.
  • XPathStringBuilder - compiles syntax tree back to XPaht string.

Installation

Install using the command line:

Install-Package XPathParser

Architecture

XPath is a language to query data from XML documents. It is built in to XSLT and can be used standalone in several .NET APIs. (http://www.w3.org/TR/xpath) In some cases customers need to parse XPath expressions themselves to analyze, modify or validate them. XPathParser is the class that can help you doing this.

To make parser extensible XPathParser uses "Builder" pattern. It takes string with XPath expression and instance of IXPathBuilder interface (builder) as input and generates set of calls to the builder.

This way implementation of the XPathParser doesn't dictate how parsed expression would be represented.

With the XPathParser we provide XPathParserTest that contains two sample implements of the IXPathBuilder: XPathTreeBuilder which builds XLinq tree as a result of parsing and XPathStringBuilder that generates string implementation of the compiled XPath.

The work of XPathParser can be demonstrated in the following diagram:

Architecture

Examples

Expression "1 + 2":

ctx = StartBuild();
return EndBuild(Operator(XPathOperator.Plus, Number(1), Number(2)))

Expression "a/@*":

ctx = StartBuild();
stp1 = Axis(ctx, XPathAxis.Child, QilXmlNodeKind.Element, "", "a");
stp2 = Axis(stp1, XPathAxis.Attribute, QilXmlNodeKind.Attribute, "", "");
return EndBuild(JoinStep(stp1, stp2));

Expression "parent:a[@b]":

ctx = StartBuild(); stp1 = Axis(ctx, XPathAxis.Parent, QilXmlNodeKind.Element, "", "a"); stp2 = Axis(stp1, XPathAxis.Attribute, QilXmlNodeKind.Attribute, "", "b"); return EndBuild(Predicate(stp1, stp2));

Credits

This repository was forked from http://xpathparser.codeplex.com/