Evaluate

IXPathEvaluator.Evaluate method

Evaluates an XPath expression string and returns a result of the specified type if possible.

public IXPathResult Evaluate(string expression, Node contextNode, IXPathNSResolver resolver, 
    XPathResultType type, object result)
Parameter Type Description
expression String The XPath expression string to be parsed and evaluated.
contextNode Node The context is context node for the evaluation of this XPath expression. If the IXPathEvaluator was obtained by casting the Document then this must be owned by the same document and must be a Document, Element, Attr, Text, CDATASection, Comment, ProcessingInstruction, or XPathNamespace node. If the context node is a Text or a CDATASection, then the context is interpreted as the whole logical text node as seen by XPath, unless the node is empty in which case it may not serve as the XPath context.
resolver IXPathNSResolver The resolver permits translation of all prefixes, including the xml namespace prefix, within the XPath expression into appropriate namespace URIs. If this is specified as null, any namespace prefix within the expression will result in DOMException being thrown with the code NAMESPACE_ERR.
type XPathResultType If a specific type is specified, then the result will be returned as the corresponding type. For XPath 1.0 results, this must be one of the values of the XPathResultType enum.
result Object The result specifies a specific result object which may be reused and returned by this method. If this is specified as null or the implementation does not reuse the specified result, a new result object will be constructed and returned. For XPath 1.0 results, this object will be of type IXPathResult.

Return Value

The result of the evaluation of the XPath expression. For XPath 1.0 results, this object will be of type IXPathResult.

Exceptions

exception condition
DOMException INVALID_EXPRESSION_ERR: Raised if the expression is not legal according to the rules of the IXPathEvaluator.
DOMException TYPE_ERR: Raised if the result cannot be converted to return the specified type.
DOMException NAMESPACE_ERR: Raised if the expression contains namespace prefixes which cannot be resolved by the specified IXPathNSResolver.
DOMException WRONG_DOCUMENT_ERR: The Node is from a document that is not supported by this IXPathEvaluator.
DOMException NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath context node or the request type is not permitted by this IXPathEvaluator.

See Also