XPathNavigator.Evaluate Method (String)

 

Evaluates the specified XPath expression and returns the typed result.

Namespace:   System.Xml.XPath
Assembly:  System.Xml (in System.Xml.dll)

abstract Evaluate : 
        xpath:string -> Object
override Evaluate : 
        xpath:string -> Object

Parameters

xpath
Type: System.String

A string representing an XPath expression that can be evaluated.

Return Value

Type: System.Object

The result of the expression (Boolean, number, string, or node set). This maps to Boolean, Double, String, or XPathNodeIterator objects respectively.

Exception Condition
ArgumentException

The return type of the XPath expression is a node set.

XPathException

The XPath expression is not valid.

The following C# code converts the Price/text() node to a number, multiplies it by 10, and returns the resulting value.

nav.Evaluate("Price/text()*10");
System_CAPS_noteNote

The XPath position() and last() functions, unless used as a predicate in a location step, require a reference to a node set in order to be evaluated. In this case, you must use the overload which takes an XPathNodeIterator as an argument; otherwise, position() and last() return 0.

This method has no effect on the state of the XPathNavigator.

The following example evaluates an XPath expression and returns a Double.

No code example is currently available or this language may not be supported.

The example takes the books.xml file as an input.


<?xml version="1.0" encoding="utf-8" ?> 
<bookstore>
    <book genre="autobiography" publicationdate="1981-03-22" ISBN="1-861003-11-0">
        <title>The Autobiography of Benjamin Franklin</title>
        <author>
            <first-name>Benjamin</first-name>
            <last-name>Franklin</last-name>
        </author>
        <price>8.99</price>
    </book>
    <book genre="novel" publicationdate="1967-11-17" ISBN="0-201-63361-2">
        <title>The Confidence Man</title>
        <author>
            <first-name>Herman</first-name>
            <last-name>Melville</last-name>
        </author>
        <price>11.99</price>
    </book>
    <book genre="philosophy" publicationdate="1991-02-15" ISBN="1-861001-57-6">
        <title>The Gorgias</title>
        <author>
            <name>Plato</name>
        </author>
        <price>9.99</price>
    </book>
</bookstore>

.NET Framework
Available since 1.1
Silverlight
Available since 4.0
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