XmlReader Class (System.Xml)

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.NET Framework Class Library

XmlReader Class

Represents a reader that provides fast, non-cached, forward-only access to XML data.

Inheritance Hierarchy

System.Object
  System.Xml.XmlReader
    System.Xml.XmlDictionaryReader
    System.Xml.XmlNodeReader
    System.Xml.XmlTextReader
    System.Xml.XmlValidatingReader

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

Syntax

Visual Basic

Public MustInherit Class XmlReader _
	Implements IDisposable

public abstract class XmlReader : IDisposable

Visual C++

public ref class XmlReader abstract : IDisposable

[<AbstractClass>]
type XmlReader =  
    class
        interface IDisposable
    end

The XmlReader type exposes the following members.

Constructors

	Name	Description
	XmlReader	Initializes a new instance of the XmlReader class.

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Properties

	Name	Description
	AttributeCount	When overridden in a derived class, gets the number of attributes on the current node.
	BaseURI	When overridden in a derived class, gets the base URI of the current node.
	CanReadBinaryContent	Gets a value indicating whether the XmlReader implements the binary content read methods.
	CanReadValueChunk	Gets a value indicating whether the XmlReader implements the ReadValueChunk method.
	CanResolveEntity	Gets a value indicating whether this reader can parse and resolve entities.
	Depth	When overridden in a derived class, gets the depth of the current node in the XML document.
	EOF	When overridden in a derived class, gets a value indicating whether the reader is positioned at the end of the stream.
	HasAttributes	Gets a value indicating whether the current node has any attributes.
	HasValue	When overridden in a derived class, gets a value indicating whether the current node can have a Value.
	IsDefault	When overridden in a derived class, gets a value indicating whether the current node is an attribute that was generated from the default value defined in the DTD or schema.
	IsEmptyElement	When overridden in a derived class, gets a value indicating whether the current node is an empty element (for example, <MyElement/>).
	Item[Int32]	When overridden in a derived class, gets the value of the attribute with the specified index.
	Item[String]	When overridden in a derived class, gets the value of the attribute with the specified Name.
	Item[String, String]	When overridden in a derived class, gets the value of the attribute with the specified LocalName and NamespaceURI.
	LocalName	When overridden in a derived class, gets the local name of the current node.
	Name	When overridden in a derived class, gets the qualified name of the current node.
	NamespaceURI	When overridden in a derived class, gets the namespace URI (as defined in the W3C Namespace specification) of the node on which the reader is positioned.
	NameTable	When overridden in a derived class, gets the XmlNameTable associated with this implementation.
	NodeType	When overridden in a derived class, gets the type of the current node.
	Prefix	When overridden in a derived class, gets the namespace prefix associated with the current node.
	QuoteChar	When overridden in a derived class, gets the quotation mark character used to enclose the value of an attribute node.
	ReadState	When overridden in a derived class, gets the state of the reader.
	SchemaInfo	Gets the schema information that has been assigned to the current node as a result of schema validation.
	Settings	Gets the XmlReaderSettings object used to create this XmlReader instance.
	Value	When overridden in a derived class, gets the text value of the current node.
	ValueType	Gets The Common Language Runtime (CLR) type for the current node.
	XmlLang	When overridden in a derived class, gets the current xml:lang scope.
	XmlSpace	When overridden in a derived class, gets the current xml:space scope.

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Methods

	Name	Description
	Close	When overridden in a derived class, changes the ReadState to Closed.
	Create(Stream)	Creates a new XmlReader instance using the specified stream.
	Create(String)	Creates a new XmlReader instance with specified URI.
	Create(TextReader)	Creates a new XmlReader instance with the specified TextReader.
	Create(Stream, XmlReaderSettings)	Creates a new XmlReader instance with the specified stream and XmlReaderSettings object.
	Create(String, XmlReaderSettings)	Creates a new instance with the specified URI and XmlReaderSettings.
	Create(TextReader, XmlReaderSettings)	Creates a new XmlReader instance using the specified TextReader and XmlReaderSettings objects.
	Create(XmlReader, XmlReaderSettings)	Creates a new XmlReader instance with the specified XmlReader and XmlReaderSettings objects.
	Create(Stream, XmlReaderSettings, String)	Creates a new XmlReader instance using the specified stream, base URI, and XmlReaderSettings object.
	Create(Stream, XmlReaderSettings, XmlParserContext)	Creates a new XmlReader instance using the specified stream, XmlReaderSettings, and XmlParserContext objects.
	Create(String, XmlReaderSettings, XmlParserContext)	Creates a new XmlReader instance using the specified URI, XmlReaderSettings, and XmlParserContext objects.
	Create(TextReader, XmlReaderSettings, String)	Creates a new XmlReader instance using the specified TextReader, XmlReaderSettings, and base URI.
	Create(TextReader, XmlReaderSettings, XmlParserContext)	Creates a new XmlReader instance using the specified TextReader, XmlReaderSettings, and XmlParserContext objects.
	Dispose()
	Dispose(Boolean)	Releases the unmanaged resources used by the XmlReader and optionally releases the managed resources.
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetAttribute(Int32)	When overridden in a derived class, gets the value of the attribute with the specified index.
	GetAttribute(String)	When overridden in a derived class, gets the value of the attribute with the specified Name.
	GetAttribute(String, String)	When overridden in a derived class, gets the value of the attribute with the specified LocalName and NamespaceURI.
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	IsName	Gets a value indicating whether the string argument is a valid XML name.
	IsNameToken	Gets a value indicating whether or not the string argument is a valid XML name token.
	IsStartElement()	Calls MoveToContent and tests if the current content node is a start tag or empty element tag.
	IsStartElement(String)	Calls MoveToContent and tests if the current content node is a start tag or empty element tag and if the Name property of the element found matches the given argument.
	IsStartElement(String, String)	Calls MoveToContent and tests if the current content node is a start tag or empty element tag and if the LocalName and NamespaceURI properties of the element found match the given strings.
	LookupNamespace	When overridden in a derived class, resolves a namespace prefix in the current element's scope.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	MoveToAttribute(Int32)	When overridden in a derived class, moves to the attribute with the specified index.
	MoveToAttribute(String)	When overridden in a derived class, moves to the attribute with the specified Name.
	MoveToAttribute(String, String)	When overridden in a derived class, moves to the attribute with the specified LocalName and NamespaceURI.
	MoveToContent	Checks whether the current node is a content (non-white space text, CDATA, Element, EndElement, EntityReference, or EndEntity) node. If the node is not a content node, the reader skips ahead to the next content node or end of file. It skips over nodes of the following type: ProcessingInstruction, DocumentType, Comment, Whitespace, or SignificantWhitespace.
	MoveToElement	When overridden in a derived class, moves to the element that contains the current attribute node.
	MoveToFirstAttribute	When overridden in a derived class, moves to the first attribute.
	MoveToNextAttribute	When overridden in a derived class, moves to the next attribute.
	Read	When overridden in a derived class, reads the next node from the stream.
	ReadAttributeValue	When overridden in a derived class, parses the attribute value into one or more Text, EntityReference, or EndEntity nodes.
	ReadContentAs	Reads the content as an object of the type specified.
	ReadContentAsBase64	Reads the content and returns the Base64 decoded binary bytes.
	ReadContentAsBinHex	Reads the content and returns the BinHex decoded binary bytes.
	ReadContentAsBoolean	Reads the text content at the current position as a Boolean.
	ReadContentAsDateTime	Reads the text content at the current position as a DateTime object.
	ReadContentAsDecimal	Reads the text content at the current position as a Decimal object.
	ReadContentAsDouble	Reads the text content at the current position as a double-precision floating-point number.
	ReadContentAsFloat	Reads the text content at the current position as a single-precision floating point number.
	ReadContentAsInt	Reads the text content at the current position as a 32-bit signed integer.
	ReadContentAsLong	Reads the text content at the current position as a 64-bit signed integer.
	ReadContentAsObject	Reads the text content at the current position as an Object.
	ReadContentAsString	Reads the text content at the current position as a String object.
	ReadElementContentAs(Type, IXmlNamespaceResolver)	Reads the element content as the requested type.
	ReadElementContentAs(Type, IXmlNamespaceResolver, String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the element content as the requested type.
	ReadElementContentAsBase64	Reads the element and decodes the Base64 content.
	ReadElementContentAsBinHex	Reads the element and decodes the BinHex content.
	ReadElementContentAsBoolean()	Reads the current element and returns the contents as a Boolean object.
	ReadElementContentAsBoolean(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a Boolean object.
	ReadElementContentAsDateTime()	Reads the current element and returns the contents as a DateTime object.
	ReadElementContentAsDateTime(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a DateTime object.
	ReadElementContentAsDecimal()	Reads the current element and returns the contents as a Decimal object.
	ReadElementContentAsDecimal(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a Decimal object.
	ReadElementContentAsDouble()	Reads the current element and returns the contents as a double-precision floating-point number.
	ReadElementContentAsDouble(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a double-precision floating-point number.
	ReadElementContentAsFloat()	Reads the current element and returns the contents as single-precision floating-point number.
	ReadElementContentAsFloat(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a single-precision floating-point number.
	ReadElementContentAsInt()	Reads the current element and returns the contents as a 32-bit signed integer.
	ReadElementContentAsInt(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a 32-bit signed integer.
	ReadElementContentAsLong()	Reads the current element and returns the contents as a 64-bit signed integer.
	ReadElementContentAsLong(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a 64-bit signed integer.
	ReadElementContentAsObject()	Reads the current element and returns the contents as an Object.
	ReadElementContentAsObject(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as an Object.
	ReadElementContentAsString()	Reads the current element and returns the contents as a String object.
	ReadElementContentAsString(String, String)	Checks that the specified local name and namespace URI matches that of the current element, then reads the current element and returns the contents as a String object.
	ReadElementString()	Reads a text-only element.
	ReadElementString(String)	Checks that the Name property of the element found matches the given string before reading a text-only element.
	ReadElementString(String, String)	Checks that the LocalName and NamespaceURI properties of the element found matches the given strings before reading a text-only element.
	ReadEndElement	Checks that the current content node is an end tag and advances the reader to the next node.
	ReadInnerXml	When overridden in a derived class, reads all the content, including markup, as a string.
	ReadOuterXml	When overridden in a derived class, reads the content, including markup, representing this node and all its children.
	ReadStartElement()	Checks that the current node is an element and advances the reader to the next node.
	ReadStartElement(String)	Checks that the current content node is an element with the given Name and advances the reader to the next node.
	ReadStartElement(String, String)	Checks that the current content node is an element with the given LocalName and NamespaceURI and advances the reader to the next node.
	ReadString	When overridden in a derived class, reads the contents of an element or text node as a string.
	ReadSubtree	Returns a new XmlReader instance that can be used to read the current node, and all its descendants.
	ReadToDescendant(String)	Advances the XmlReader to the next descendant element with the specified qualified name.
	ReadToDescendant(String, String)	Advances the XmlReader to the next descendant element with the specified local name and namespace URI.
	ReadToFollowing(String)	Reads until an element with the specified qualified name is found.
	ReadToFollowing(String, String)	Reads until an element with the specified local name and namespace URI is found.
	ReadToNextSibling(String)	Advances the XmlReader to the next sibling element with the specified qualified name.
	ReadToNextSibling(String, String)	Advances the XmlReader to the next sibling element with the specified local name and namespace URI.
	ReadValueChunk	Reads large streams of text embedded in an XML document.
	ResolveEntity	When overridden in a derived class, resolves the entity reference for EntityReference nodes.
	Skip	Skips the children of the current node.
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Explicit Interface Implementations

	Name	Description
	IDisposable.Dispose	For a description of this member, see IDisposable.Dispose.

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Remarks

XmlReader provides forward-only, read-only access to a stream of XML data. The XmlReader class conforms to the W3C Extensible Markup Language (XML) 1.0 and the Namespaces in XML recommendations.

The current node refers to the node on which the reader is positioned. The reader is advanced using any of the read methods and properties reflect the value of the current node.

Important
Although the Microsoft .NET Framework includes concrete implementations of the XmlReader class, such as the XmlTextReader, XmlNodeReader, and the XmlValidatingReader classes, in the 2.0 release the recommended practice is to create XmlReader instances using the Create method. For more information, see Creating XML Readers.

XmlReader throws an XmlException on XML parse errors. After an exception is thrown the state of the reader is not predictable. For example, the reported node type may be different than the actual node type of the current node. Use the ReadState property to check whether the reader is in error state.

For further discussion on the XmlReader class, see Reading XML with the XmlReader.

Security Considerations

The following items are things to consider when working with the XmlReader class.

Exceptions thrown the XmlReader can disclose path information that you do not want bubbled up to the application. Your applications must catch exceptions and process them appropriately.
Do not enable DTD processing if you are concerned about denial of service issues or if you are dealing with untrusted sources. DTD processing is disabled by default for XmlReader objects created by the Create method.

If you have DTD processing enabled, you can use the XmlSecureResolver to restrict the resources that the XmlReader can access. You can also design your application so that the XML processing is memory and time constrained. For example, configure time-out limits in your ASP.NET application.
XML data can include references to external resources such as a schema file. By default external resources are resolved using an XmlUrlResolver object with no user credentials. You can secure this further by doing one of the following:
- Restrict the resources that the XmlReader can access by setting the XmlReaderSettings.XmlResolver property to an XmlSecureResolver object.
- Do not allow the XmlReader to open any external resources by setting the XmlReaderSettings.XmlResolver property to null.
XML data can contain a large number of attributes, namespace declarations, nested elements and so on that require a substantial amount of time to process. To limit the size of the input that is sent to the XmlReader, create a custom IStream implementation and supply it the XmlReader.
The ReadValueChunk method can be used to handle large streams of data. This method reads a small number of characters at a time instead of allocating a single string for the whole value.
When reading an XML document with a large number of unique local names, namespaces, or prefixes, a problem can occur. If you are using a class that derives from XmlReader, and you call either the LocalName, Prefix, or NamespaceURI property for each item, the returned string is added to a NameTable. The collection held by the NameTable never decreases in size, creating a virtual "memory leak" of the string handles. One mitigation for this is to derive from the NameTable class and enforce a maximum size quota. (There is no way to prevent the use of a NameTable, or to switch the NameTable when it is full). Another mitigation is to avoid using the properties mentioned and instead use the MoveToAttribute method with the IsStartElement method where possible; those methods do not return strings and thus avoid the problem of overfilling the NameTable collection.

Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Reference

System.Xml Namespace

Other Resources

XML Documents and Data

Security and Your System.Xml Applications

Community Content

masbaaz

Disposing XmlReader object

you can explicitly cast the XMLReader object to System.IDisposable inorder to gain access to Dispose() method.

For example:

suppose we have belowScenario:

            XmlReader reader = XmlReader.Create("ServiceReferences.ClientConfig");

            reader.MoveToContent();

            while (reader.Read())

            {

                // DO your logic and processing

            }

//Then proceed to dispose as below:

((System.IDisposable)(reader)).Dispose();

((System.IDisposable)(reader)).Dispose();

This is how you can dispose XmlReader object by explicityly casting to (System.IDisposable)

HerbF

Wrap inside a using statement to dispose

You can also wrap it within a using statement to dispose of it. No need to cast in this case.

webJose

The parameterless Dispose() method is not public

I guess htis is a documentation bug. The parameterless Dispose() method is not public.

Incorrect. Dispose() is public, but you must read carefully: The interface implementation is explicit. You must explicitly cast the object to IDisposable in order to gain access to Dispose().

webJose

Dispoe() is not public

I guess the documentation has a bug the no parameter Dispose() method on XmlReader is not public.

Incorrect. Dispose() is public, but you must read carefully: The interface implementation is explicit. You must explicitly cast the object to IDisposable in order to gain access to Dispose().

Jamie A. Hankins

Dispose...

Nothing stops you from casting it to IDisposable and calling Dispose, right?