### Saxon.Api

- BinaryResource
- CatalogCollection
- DirectoryCollection
- DocumentBuilder
- DomDestination
- DynamicContext
- DynamicError
- EmptyEnumerator<T>
- ErrorReporter
- ErrorReporterToStaticError
- ErrorReporterWrapper
- ExtensionFunction
- ExtensionFunctionCall
- ExtensionFunctionDefinition
- Feature<T>
- FeatureKeys
- HostLanguage
- ICollectionFinder
- IErrorReporter
- IInvalidityHandler
- IMessageListener
- IMessageListener2
- InvalidityHandlerWrapper
- IPredicate<in XdmItem>
- IQueryResolver
- IResource
- IResourceCollection
- IResourceFactory
- IResultDocumentHandler
- IXmlLocation
- JarCollection
- NamespaceConstant
- NullDestination
- Predicate<T>
- Predicates
- Processor
- QName
- RawDestination
- RecoveryPolicy
- Resource
- ResourceCollection
- SchemaManager
- SchemaResolver
- SchemaValidationMode
- SchemaValidator
- Serializer
- StandardCollectionFinder
- StandardLogger
- StaticContext
- StaticError
- Step<TInput, TResult>
- Steps
- TextWriterDestination
- TreeModel
- URIQueryParameters
- ValidationFailure
- WhitespacePolicy
- XdmAnyArrayType
- XdmAnyFunctionType
- XdmAnyItemType
- XdmAnyMapType
- XdmAnyNodeType
- XdmArray
- XdmAtomicType
- XdmAtomicValue
- XdmAxis
- XdmDestination
  - - TreeProtector
- XdmEmptySequence
- XdmExternalObjectValue
- XdmFunctionItem
- XdmItem
- XdmItemType
- XdmMap
- XdmNode
- XdmNodeKind
- XdmSequenceType
- XdmValue
- XmlDestination
- XmlProcessingError
- XmlResource
- XPathCompiler
- XPathExecutable
- XPathSelector
- XQueryCompiler
- XQueryEvaluator
- XQueryExecutable
- Xslt30Transformer
- XsltCompiler
- XsltExecutable
  - - ParameterDetails
- XsltPackage
- XsltTransformer

### Saxon.Api

# Class XPathSelector

public class XPathSelector
implements IEnumerable

An `XPathSelector` represents a compiled and loaded XPath expression ready for execution. The `XPathSelector` holds details of the dynamic evaluation context for the XPath expression.

An `XPathSelector` should not be used concurrently in multiple threads. It is safe, however, to reuse the object within a single thread to evaluate the same XPath expression several times. Evaluating the expression does not change the context that has been established.

An `XPathSelector` is always constructed by running the `Load` method of an `XPathExecutable`.

The class `XPathSelector` implements `IEnumerable`, so it is possible to enumerate the results in a `for` expression.

### Property Summary
XdmItem | ContextItem The context item for the XPath expression evaluation.
net.sf.saxon.s9api.XPathSelector | Implementation Escape hatch to the `net.sf.saxon.s9api.XPathSelector` object in the underlying Java implementation
XmlResolver | InputXmlResolver The `XmlResolver` to be used at run-time to resolve and dereference URIs supplied to the `doc()` function.

### Method Summary
bool | EffectiveBooleanValue() Evaluate the effective boolean value of the XPath expression, returning the result as a `Boolean`
XdmValue | Evaluate() Evaluate the expression, returning the result as an `XdmValue` (that is, a sequence of nodes, atomic values, and possibly function items such as maps and arrays).
XdmItem | EvaluateSingle() Evaluate the XPath expression, returning the result as an `XdmItem` (that is, a single node or atomic value).
IEnumerator | GetEnumerator() Evaluate the expression, returning the result as an `IEnumerator` (that is, an enumerator over a sequence of nodes and/or atomic values).
void | SetVariable(QName name, XdmValue value) Set the value of a variable

## Property Detail

### ContextItem

public XdmItem ContextItem {get; set; }

The context item for the XPath expression evaluation.

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

### Implementation

public net.sf.saxon.s9api.XPathSelector Implementation {get; }

Escape hatch to the `net.sf.saxon.s9api.XPathSelector` object in the underlying Java implementation

### InputXmlResolver

public XmlResolver InputXmlResolver {get; set; }

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

## Method Detail

### EffectiveBooleanValue

public bool EffectiveBooleanValue()
throws
DynamicError

Evaluate the effective boolean value of the XPath expression, returning the result as a `Boolean`

Returns:

A `Boolean` representing the result of the expression, converted to its effective boolean value as if by applying the XPath `boolean()` function

Throws:

DynamicError - Throws `Saxon.Api.DynamicError` if the evaluation of the XPath expression fails with a dynamic error.

### Evaluate

public XdmValue Evaluate()
throws
DynamicError

Evaluate the expression, returning the result as an `XdmValue` (that is, a sequence of nodes, atomic values, and possibly function items such as maps and arrays).

Although a singleton result may be represented as an `XdmItem`, there is no guarantee that this will always be the case. If you know that the expression will return at most one node or atomic value, it is best to use the `EvaluateSingle` method, which does guarantee that an `XdmItem` (or null) will be returned.

Returns:

An `XdmValue` representing the results of the expression.

Throws:

DynamicError - Throws `Saxon.Api.DynamicError` if the evaluation of the XPath expression fails with a dynamic error.

### EvaluateSingle

public XdmItem EvaluateSingle()
throws
DynamicError

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

Returns:

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

Throws:

DynamicError - Throws `Saxon.Api.DynamicError` if the evaluation of the XPath expression fails with a dynamic error.

### GetEnumerator

public IEnumerator GetEnumerator()
throws
DynamicError

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

Throws:

DynamicError - May throw a `Saxon.Api.DynamicError` if the evaluation of the XPath expression fails with a dynamic error. However, some errors will not be detected during the invocation of this method, but only when stepping through the returned `SequenceEnumerator`.

### SetVariable

public void SetVariable(QName name,
XdmValue value)

Set the value of a variable

Parameters:

`name` - The name of the variable. This must match the name of a variable that was declared to the `XPathCompiler`. No error occurs if the expression does not actually reference a variable with this name.
`value` - The value to be given to the variable.