Windows Dev Center

XmlReader Class

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

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

public abstract class XmlReader : IDisposable

The XmlReader type exposes the following members.

  NameDescription
Protected methodXmlReaderInitializes a new instance of the XmlReader class.
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  NameDescription
Public propertyAttributeCountWhen overridden in a derived class, gets the number of attributes on the current node.
Public propertyBaseURIWhen overridden in a derived class, gets the base URI of the current node.
Public propertyCanReadBinaryContentGets a value indicating whether the XmlReader implements the binary content read methods.
Public propertyCanReadValueChunkGets a value indicating whether the XmlReader implements the ReadValueChunk method.
Public propertyCanResolveEntityGets a value indicating whether this reader can parse and resolve entities.
Public propertyDepthWhen overridden in a derived class, gets the depth of the current node in the XML document.
Public propertyEOFWhen overridden in a derived class, gets a value indicating whether the reader is positioned at the end of the stream.
Public propertyHasAttributesGets a value indicating whether the current node has any attributes.
Public propertyHasValueWhen overridden in a derived class, gets a value indicating whether the current node can have a Value.
Public propertyIsDefaultWhen 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.
Public propertyIsEmptyElementWhen overridden in a derived class, gets a value indicating whether the current node is an empty element (for example, <MyElement/>).
Public propertyItem[Int32]When overridden in a derived class, gets the value of the attribute with the specified index.
Public propertyItem[String]When overridden in a derived class, gets the value of the attribute with the specified Name.
Public propertyItem[String, String]When overridden in a derived class, gets the value of the attribute with the specified LocalName and NamespaceURI.
Public propertyLocalNameWhen overridden in a derived class, gets the local name of the current node.
Public propertyNameWhen overridden in a derived class, gets the qualified name of the current node.
Public propertyNamespaceURIWhen 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.
Public propertyNameTableWhen overridden in a derived class, gets the XmlNameTable associated with this implementation.
Public propertyNodeTypeWhen overridden in a derived class, gets the type of the current node.
Public propertyPrefixWhen overridden in a derived class, gets the namespace prefix associated with the current node.
Public propertyReadStateWhen overridden in a derived class, gets the state of the reader.
Public propertySettingsGets the XmlReaderSettings object used to create this XmlReader instance.
Public propertyValueWhen overridden in a derived class, gets the text value of the current node.
Public propertyValueTypeGets the common language runtime (CLR) type for the current node.
Public propertyXmlLangWhen overridden in a derived class, gets the current xml:lang scope.
Public propertyXmlSpaceWhen overridden in a derived class, gets the current xml:space scope.
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  NameDescription
Public methodCloseWhen overridden in a derived class, changes the ReadState to Closed.
Public methodStatic memberCreate(Stream)Creates a new XmlReader instance using the specified stream.
Public methodStatic memberCreate(String)Creates a new XmlReader instance with specified URI.
Public methodStatic memberCreate(TextReader)Creates a new XmlReader instance with the specified TextReader.
Public methodStatic memberCreate(Stream, XmlReaderSettings)Creates a new XmlReader instance with the specified stream and XmlReaderSettings object.
Public methodStatic memberCreate(String, XmlReaderSettings)Creates a new instance with the specified URI and XmlReaderSettings.
Public methodStatic memberCreate(TextReader, XmlReaderSettings)Creates a new XmlReader instance using the specified TextReader and XmlReaderSettings objects.
Public methodStatic memberCreate(XmlReader, XmlReaderSettings)Creates a new XmlReader instance with the specified XmlReader and XmlReaderSettings objects.
Public methodStatic memberCreate(Stream, XmlReaderSettings, String)Creates a new XmlReader instance using the specified stream, base URI, and XmlReaderSettings object.
Public methodStatic memberCreate(Stream, XmlReaderSettings, XmlParserContext)Creates a new XmlReader instance using the specified stream, XmlReaderSettings, and XmlParserContext objects.
Public methodStatic memberCreate(String, XmlReaderSettings, XmlParserContext)Creates a new XmlReader instance using the specified URI, XmlReaderSettings, and XmlParserContext objects.
Public methodStatic memberCreate(TextReader, XmlReaderSettings, String)Creates a new XmlReader instance using the specified TextReader, XmlReaderSettings, and base URI.
Public methodStatic memberCreate(TextReader, XmlReaderSettings, XmlParserContext)Creates a new XmlReader instance using the specified TextReader, XmlReaderSettings, and XmlParserContext objects.
Public methodDispose()Releases all resources used by the current instance of the XmlReader class.
Protected methodDispose(Boolean)Releases the unmanaged resources used by the XmlReader and optionally releases the managed resources.
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetAttribute(Int32)When overridden in a derived class, gets the value of the attribute with the specified index.
Public methodGetAttribute(String)When overridden in a derived class, gets the value of the attribute with the specified Name.
Public methodGetAttribute(String, String)When overridden in a derived class, gets the value of the attribute with the specified LocalName and NamespaceURI.
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodGetValueAsyncAsynchronously gets the value of the current node.
Public methodStatic memberIsNameGets a value indicating whether the string argument is a valid XML name.
Public methodStatic memberIsNameTokenGets a value indicating whether or not the string argument is a valid XML name token.
Public methodIsStartElement()Calls MoveToContent and tests if the current content node is a start tag or empty element tag.
Public methodIsStartElement(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.
Public methodIsStartElement(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.
Public methodLookupNamespaceWhen overridden in a derived class, resolves a namespace prefix in the current element's scope.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodMoveToAttribute(Int32)When overridden in a derived class, moves to the attribute with the specified index.
Public methodMoveToAttribute(String)When overridden in a derived class, moves to the attribute with the specified Name.
Public methodMoveToAttribute(String, String)When overridden in a derived class, moves to the attribute with the specified LocalName and NamespaceURI.
Public methodMoveToContentChecks 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.
Public methodMoveToContentAsyncAsynchronously checks whether the current node is a content node. If the node is not a content node, the reader skips ahead to the next content node or end of file.
Public methodMoveToElementWhen overridden in a derived class, moves to the element that contains the current attribute node.
Public methodMoveToFirstAttributeWhen overridden in a derived class, moves to the first attribute.
Public methodMoveToNextAttributeWhen overridden in a derived class, moves to the next attribute.
Public methodReadWhen overridden in a derived class, reads the next node from the stream.
Public methodReadAsyncAsynchronously reads the next node from the stream.
Public methodReadAttributeValueWhen overridden in a derived class, parses the attribute value into one or more Text, EntityReference, or EndEntity nodes.
Public methodReadContentAsReads the content as an object of the type specified.
Public methodReadContentAsAsyncAsynchronously reads the content as an object of the type specified.
Public methodReadContentAsBase64Reads the content and returns the Base64 decoded binary bytes.
Public methodReadContentAsBase64AsyncAsynchronously reads the content and returns the Base64 decoded binary bytes.
Public methodReadContentAsBinHexReads the content and returns the BinHex decoded binary bytes.
Public methodReadContentAsBinHexAsyncAsynchronously reads the content and returns the BinHex decoded binary bytes.
Public methodReadContentAsBooleanReads the text content at the current position as a Boolean.
Public methodReadContentAsDateTimeReads the text content at the current position as a DateTime object.
Public methodReadContentAsDateTimeOffsetReads the text content at the current position as a DateTimeOffset object.
Public methodReadContentAsDecimalReads the text content at the current position as a Decimal object.
Public methodReadContentAsDoubleReads the text content at the current position as a double-precision floating-point number.
Public methodReadContentAsFloatReads the text content at the current position as a single-precision floating point number.
Public methodReadContentAsIntReads the text content at the current position as a 32-bit signed integer.
Public methodReadContentAsLongReads the text content at the current position as a 64-bit signed integer.
Public methodReadContentAsObjectReads the text content at the current position as an Object.
Public methodReadContentAsObjectAsyncAsynchronously reads the text content at the current position as an Object.
Public methodReadContentAsStringReads the text content at the current position as a String object.
Public methodReadContentAsStringAsyncAsynchronously reads the text content at the current position as a String object.
Public methodReadElementContentAs(Type, IXmlNamespaceResolver)Reads the element content as the requested type.
Public methodReadElementContentAs(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.
Public methodReadElementContentAsAsyncAsynchronously reads the element content as the requested type.
Public methodReadElementContentAsBase64Reads the element and decodes the Base64 content.
Public methodReadElementContentAsBase64AsyncAsynchronously reads the element and decodes the Base64 content.
Public methodReadElementContentAsBinHexReads the element and decodes the BinHex content.
Public methodReadElementContentAsBinHexAsyncAsynchronously reads the element and decodes the BinHex content.
Public methodReadElementContentAsBoolean()Reads the current element and returns the contents as a Boolean object.
Public methodReadElementContentAsBoolean(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.
Public methodReadElementContentAsDateTime()Reads the current element and returns the contents as a DateTime object.
Public methodReadElementContentAsDateTime(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.
Public methodReadElementContentAsDecimal()Reads the current element and returns the contents as a Decimal object.
Public methodReadElementContentAsDecimal(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.
Public methodReadElementContentAsDouble()Reads the current element and returns the contents as a double-precision floating-point number.
Public methodReadElementContentAsDouble(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.
Public methodReadElementContentAsFloat()Reads the current element and returns the contents as single-precision floating-point number.
Public methodReadElementContentAsFloat(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.
Public methodReadElementContentAsInt()Reads the current element and returns the contents as a 32-bit signed integer.
Public methodReadElementContentAsInt(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.
Public methodReadElementContentAsLong()Reads the current element and returns the contents as a 64-bit signed integer.
Public methodReadElementContentAsLong(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.
Public methodReadElementContentAsObject()Reads the current element and returns the contents as an Object.
Public methodReadElementContentAsObject(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.
Public methodReadElementContentAsObjectAsyncAsynchronously reads the current element and returns the contents as an Object.
Public methodReadElementContentAsString()Reads the current element and returns the contents as a String object.
Public methodReadElementContentAsString(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.
Public methodReadElementContentAsStringAsyncAsynchronously reads the current element and returns the contents as a String object.
Public methodReadEndElementChecks that the current content node is an end tag and advances the reader to the next node.
Public methodReadInnerXmlWhen overridden in a derived class, reads all the content, including markup, as a string.
Public methodReadInnerXmlAsyncAsynchronously reads all the content, including markup, as a string.
Public methodReadOuterXmlWhen overridden in a derived class, reads the content, including markup, representing this node and all its children.
Public methodReadOuterXmlAsyncAsynchronously reads the content, including markup, representing this node and all its children.
Public methodReadStartElement()Checks that the current node is an element and advances the reader to the next node.
Public methodReadStartElement(String)Checks that the current content node is an element with the given Name and advances the reader to the next node.
Public methodReadStartElement(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.
Public methodReadSubtreeReturns a new XmlReader instance that can be used to read the current node, and all its descendants.
Public methodReadToDescendant(String)Advances the XmlReader to the next descendant element with the specified qualified name.
Public methodReadToDescendant(String, String)Advances the XmlReader to the next descendant element with the specified local name and namespace URI.
Public methodReadToFollowing(String)Reads until an element with the specified qualified name is found.
Public methodReadToFollowing(String, String)Reads until an element with the specified local name and namespace URI is found.
Public methodReadToNextSibling(String)Advances the XmlReader to the next sibling element with the specified qualified name.
Public methodReadToNextSibling(String, String)Advances the XmlReader to the next sibling element with the specified local name and namespace URI.
Public methodReadValueChunkReads large streams of text embedded in an XML document.
Public methodReadValueChunkAsyncAsynchronously reads large streams of text embedded in an XML document.
Public methodResolveEntityWhen overridden in a derived class, resolves the entity reference for EntityReference nodes.
Public methodSkipSkips the children of the current node.
Public methodSkipAsyncAsynchronously skips the children of the current node.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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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 noteImportant Note:

You must use Create method to create XmlReader instances.

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.

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.

    You can 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 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 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 Notes

Windows Phone

  XmlReader does not fail when numeric character entity computation overflows. Instead, an empty string is returned to Value.

The following example navigates through the stream to determine the current node type, and then uses XmlWriter to output the XmlReader content.


StringBuilder output = new StringBuilder();

String xmlString =
        @"<?xml version='1.0'?>
        <!-- This is a sample XML document -->
        <Items>
          <Item>test with a child element <more/> stuff</Item>
        </Items>";
// Create an XmlReader
using (XmlReader reader = XmlReader.Create(new StringReader(xmlString)))
{
    XmlWriterSettings ws = new XmlWriterSettings();
    ws.Indent = true;
    using (XmlWriter writer = XmlWriter.Create(output, ws))
    {

        // Parse the file and display each of the nodes.
        while (reader.Read())
        {
            switch (reader.NodeType)
            {
                case XmlNodeType.Element:
                    writer.WriteStartElement(reader.Name);
                    break;
                case XmlNodeType.Text:
                    writer.WriteString(reader.Value);
                    break;
                case XmlNodeType.XmlDeclaration:
                case XmlNodeType.ProcessingInstruction:
                    writer.WriteProcessingInstruction(reader.Name, reader.Value);
                    break;
                case XmlNodeType.Comment:
                    writer.WriteComment(reader.Value);
                    break;
                case XmlNodeType.EndElement:
                    writer.WriteFullEndElement();
                    break;
            }
        }

    }
}
OutputTextBlock.Text = output.ToString();


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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

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