Artículo
11/18/2011

XAttribute Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Represents an XML attribute.

Inheritance Hierarchy

System.Object
System.Xml.Linq.XObject
System.Xml.Linq.XAttribute

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

Syntax

'Declaration
Public Class XAttribute _
    Inherits XObject

public class XAttribute : XObject

The XAttribute type exposes the following members.

Constructors

	Name	Description
	XAttribute(XAttribute)	Initializes a new instance of the XAttribute class from another XAttribute object.
	XAttribute(XName, Object)	Initializes a new instance of the XAttribute class from the specified name and value.

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Properties

	Name	Description
	BaseUri	Gets the base URI for this XObject. (Inherited from XObject.)
	Document	Gets the XDocument for this XObject. (Inherited from XObject.)
	EmptySequence	Gets an empty collection of attributes.
	IsNamespaceDeclaration	Determines if this attribute is a namespace declaration.
	Name	Gets the expanded name of this attribute.
	NextAttribute	Gets the next attribute of the parent element.
	NodeType	Gets the node type for this node. (Overrides XObject.NodeType.)
	Parent	Gets the parent XElement of this XObject. (Inherited from XObject.)
	PreviousAttribute	Gets the previous attribute of the parent element.
	Value	Gets or sets the value of this attribute.

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Methods

	Name	Description
	AddAnnotation	Adds an object to the annotation list of this XObject. (Inherited from XObject.)
	Annotation(Type)	Gets the first annotation object of the specified type from this XObject. (Inherited from XObject.)
	Annotation<T>()	Get the first annotation object of the specified type from this XObject. (Inherited from XObject.)
	Annotations(Type)	Gets a collection of annotations of the specified type for this XObject. (Inherited from XObject.)
	Annotations<T>()	Gets a collection of annotations of the specified type for this XObject. (Inherited from XObject.)
	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 the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	Remove	Removes this attribute from its parent element.
	RemoveAnnotations(Type)	Removes the annotations of the specified type from this XObject. (Inherited from XObject.)
	RemoveAnnotations<T>()	Removes the annotations of the specified type from this XObject. (Inherited from XObject.)
	SetValue	Sets the value of this attribute.
	ToString	Converts the current XAttribute object to a string representation. (Overrides Object.ToString().)

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Events

	Name	Description
	Changed	Raised when this XObject or any of its descendants have changed. (Inherited from XObject.)
	Changing	Raised when this XObject or any of its descendants are about to change. (Inherited from XObject.)

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Operators

	Name	Description
	Explicit(XAttribute to DateTime)	Cast the value of this XAttribute to a DateTime.
	Explicit(XAttribute to Nullable<DateTime>)	Cast the value of this XAttribute to a Nullable<T> of DateTime.
	Explicit(XAttribute to Nullable<Decimal>)	Cast the value of this XAttribute to a Nullable<T> of Decimal.
	Explicit(XAttribute to Nullable<Double>)	Cast the value of this XAttribute to a Nullable<T> of Double.
	Explicit(XAttribute to Decimal)	Cast the value of this XAttribute to a Decimal.
	Explicit(XAttribute to DateTimeOffset)	Cast the value of this XAttribute to a DateTimeOffset.
	Explicit(XAttribute to Guid)	Cast the value of this XAttribute to a Guid.
	Explicit(XAttribute to Nullable<Guid>)	Cast the value of this XAttribute to a Nullable<T> of Guid.
	Explicit(XAttribute to Nullable<TimeSpan>)	Cast the value of this XAttribute to a Nullable<T> of TimeSpan.
	Explicit(XAttribute to Nullable<DateTimeOffset>)	Cast the value of this XAttribute to a Nullable<T> of DateTimeOffset.
	Explicit(XAttribute to TimeSpan)	Cast the value of this XAttribute to a TimeSpan.
	Explicit(XAttribute to Double)	Cast the value of this XAttribute to a Double.
	Explicit(XAttribute to Int32)	Cast the value of this XAttribute to an Int32.
	Explicit(XAttribute to Nullable<Int32>)	Cast the value of this XAttribute to a Nullable<T> of Int32.
	Explicit(XAttribute to UInt32)	Cast the value of this XAttribute to a UInt32.
	Explicit(XAttribute to String)	Cast the value of this XAttribute to a String.
	Explicit(XAttribute to Boolean)	Cast the value of this XAttribute to a Boolean.
	Explicit(XAttribute to Nullable<Boolean>)	Cast the value of this XAttribute to a Nullable<T> of Boolean.
	Explicit(XAttribute to Nullable<UInt32>)	Cast the value of this XAttribute to a Nullable<T> of UInt32.
	Explicit(XAttribute to Nullable<UInt64>)	Cast the value of this XAttribute to a Nullable<T> of UInt64.
	Explicit(XAttribute to Single)	Cast the value of this XAttribute to a Single.
	Explicit(XAttribute to Nullable<Single>)	Cast the value of this XAttribute to a Nullable<T> of Single.
	Explicit(XAttribute to Int64)	Cast the value of this XAttribute to an Int64.
	Explicit(XAttribute to Nullable<Int64>)	Cast the value of this XAttribute to a Nullable<T> of Int64.
	Explicit(XAttribute to UInt64)	Cast the value of this XAttribute to a UInt64.

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Explicit Interface Implementations

	Name	Description
	IXmlLineInfo.HasLineInfo	Gets a value indicating whether or not this XObject has line information. (Inherited from XObject.)
	IXmlLineInfo.LineNumber	Gets the line number that the underlying XmlReader reported for this XObject. (Inherited from XObject.)
	IXmlLineInfo.LinePosition	Gets the line position that the underlying XmlReader reported for this XObject. (Inherited from XObject.)

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Remarks

An XML attribute is a name/value pair associated with an XML element.

Each XElement contains a list of the attributes for that element. Attributes must have a qualified name that is unique to the element. Attributes are not derived from XNode; they are not nodes in the XML tree. Instead, they are simply name/value pairs associated with an element.

Attributes are maintained in the XML tree in the order that they were added to the element. When a collection of attributes is returned by Attributes, they are returned in the order that they were added to the element, and are not sorted.

Technically, in XML, namespace declarations are not attributes proper. However, this distinction is not normally made by many XML programmers. Instead, because namespace declarations have exactly the same XML syntax as attributes, most XML programmers think of namespaces as attributes. To simplify the LINQ to XML programming interface, namespaces are represented in the XML tree as attributes. Such namespace attributes impact serialization of an XML tree. When serializing, LINQ to XML attempts to serialize with the namespace prefix specified in namespace attributes. You can use the IsNamespaceDeclaration to determine if an attribute is really a namespace declaration.

The XAttribute class derives from XObject. You can add annotations to attributes, and observe events for them.

Some XAttribute methods can be used from XAML, for more information, see LINQ to XML Dynamic Properties in the .NET Framework documentation.

Examples

The following example uses this constructor to create attributes. It passes strings as the first argument to the XAttribute constructor, which are then implicitly converted to XName objects. The attributes are added to an element.

Dim output As New StringBuilder
Dim dbl As Double = 12.345
Dim attArray As XAttribute() = { _
    New XAttribute("Att4", 1), _
    New XAttribute("Att5", 2), _
    New XAttribute("Att6", 3) _
}
Dim dt As DateTime = New DateTime(2006, 10, 6, 12, 30, 0)
Dim root As XElement = <Root Att1="Some text"
                           Att2=<%= dbl %>
                           Att3=<%= dt %>
                           <%= attArray %>
                       />
output.Append(root)
output.Append(Environment.NewLine)

OutputTextBlock.Text = output.ToString()

    StringBuilder output = new StringBuilder();
    XElement root;

    double dbl = 12.345;
    XAttribute[] attArray = {
    new XAttribute("Att4", 1),
    new XAttribute("Att5", 2),
    new XAttribute("Att6", 3)
};
    DateTime dt = new DateTime(2006, 10, 6, 12, 30, 00);

    // string content
    root = new XElement("Root",
        new XAttribute("Att1", "Some text"),

        // double content
        new XAttribute("Att2", dbl),

        // DateTime content
        new XAttribute("Att3", dt),

        // XAttribute array content
        attArray
    );

    output.Append(root + Environment.NewLine);

    OutputTextBlock.Text = output.ToString();

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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.

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