XQueryEvaluator

Saxon.Api
Class XQueryEvaluator

public class XQueryEvaluator
implements IEnumerable

An XQueryEvaluator represents a compiled and loaded query ready for execution. The XQueryEvaluator holds details of the dynamic evaluation context for the query.

An XQueryEvaluator should not be used concurrently in multiple threads. It is safe, however, to reuse the object within a single thread to run the same query several times. Running the query does not change the context that has been established.

An XQueryEvaluator is always constructed by running the Load method of an XQueryExecutable.

Property Summary
`XdmItem`	`ContextItem` The context item for the query.
	`SchemaValidationMode` The `SchemaValidationMode` to be used in this transformation, especially for documents loaded using the `doc()`, `document()`, or `collection()` functions.
`XmlResolver`	`InputXmlResolver` The `XmlResolver` to be used at run-time to resolve and dereference URIs supplied to the `doc()` function.
`Stream`	`TraceFunctionDestination` Destination for output of messages produced using <trace()>. If no specific destination is supplied by the caller, message information will be written to the standard error stream.

Method Summary
`void`	`SetExternalVariable(QName name, XdmValue value)` Set the value of an external variable declared in the query.
`XdmValue`	`Evaluate()` Evaluate the query, returning the result as an `XdmValue` (that is, a sequence of nodes and/or atomic values).
`XdmItem`	`EvaluateSingle()` Evaluate the query, returning the result as an `XdmItem` (that is, a single node or atomic value).
`IEnumerator`	`GetEnumerator()` Evaluate the query, returning the result as an `IEnumerator` (that is, an enumerator over a sequence of nodes and/or atomic values).
`void`	`Run(XmlDestination destination)` Evaluate the query, sending the result to a specified destination.
`XdmNode[]`	`RunUpdate()` Execute an updating query.

Property Detail

ContextItem

public XdmItem ContextItem {get; set; }

The context item for the query.

This may be either a node or an atomic value. Most commonly it will be a document node, which might be constructed using the LoadDocument method of the Processor object.

SchemaValidationMode

public  SchemaValidationMode {get; set; }

The SchemaValidationMode to be used in this transformation, especially for documents loaded using the doc(), document(), or collection() functions.

InputXmlResolver

public XmlResolver InputXmlResolver {get; set; }

The XmlResolver to be used at run-time to resolve and dereference URIs supplied to the doc() function.

TraceFunctionDestination

public Stream TraceFunctionDestination {get; set; }

Destination for output of messages produced using <trace()>.

If no specific destination is supplied by the caller, message information will be written to the standard error stream.

The supplied destination is ignored if a TraceListener is in use.

Property added in Saxon 9.1

Method Detail

SetExternalVariable

public void SetExternalVariable(QName name,
                           XdmValue value)

Set the value of an external variable declared in the query.

Parameters:

name -: The name of the external variable, expressed as a QName. If an external variable of this name has been declared in the query prolog, the given value will be assigned to the variable. If the variable has not been declared, calling this method has no effect (it is not an error).

value -: The value to be given to the external variable. If the variable declaration defines a required type for the variable, then this value must match the required type: no conversions are applied.

Evaluate

public XdmValue Evaluate()

Evaluate the query, returning the result as an XdmValue (that is, a sequence of nodes and/or atomic values).

returns: An XdmValue representing the results of the query

EvaluateSingle

public XdmItem EvaluateSingle()

Evaluate the query, returning the result as an XdmItem (that is, a single node or atomic value).

returns: An XdmItem representing the result of the query, or null if the query returns an empty sequence. If the query returns a sequence of more than one item, any items after the first are ignored.

GetEnumerator

public IEnumerator GetEnumerator()

Evaluate the query, returning the result as an IEnumerator (that is, an enumerator over a sequence of nodes and/or atomic values).

returns: An enumerator over the sequence that represents the results of the query. Each object in this sequence will be an instance of XdmItem. Note that the query may be evaluated lazily, which means that a successful response from this method does not imply that the query has executed successfully: failures may be reported later while retrieving items from the iterator.

Run

public void Run(XmlDestination destination)

Evaluate the query, sending the result to a specified destination.