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Learn more about: XML Element Literal (Visual Basic)
XML Element Literal
07/20/2015
vb.XmlLiteralElement
XML element literal [Visual Basic]
element literal [Visual Basic]
XML literals [Visual Basic], element
95039642-7893-48b7-b23f-45a6c55d8f67

XML Element Literal (Visual Basic)

A literal that represents an xref:System.Xml.Linq.XElement object.

Syntax

<name [ attributeList ] />
-or-
<name [ attributeList ] > [ elementContents ] </[ name ]>

Parts

  • <

    Required. Opens the starting element tag.

  • name

    Required. Name of the element. The format is one of the following:

    • Literal text for the element name, of the form [ePrefix:]eName, where:

      Part Description
      ePrefix Optional. XML namespace prefix for the element. Must be a global XML namespace that is defined with an Imports statement in the file or at the project level, or a local XML namespace that is defined in this element or a parent element.
      eName Required. Name of the element. The format is one of the following:

      - Literal text. See Names of Declared XML Elements and Attributes.
      - Embedded expression of the form <%= eNameExp %>. The type of eNameExp must be String or a type that is implicitly convertible to xref:System.Xml.Linq.XName.

    • Embedded expression of the form <%= nameExp %>. The type of nameExp must be String or a type implicitly convertible to xref:System.Xml.Linq.XName. An embedded expression is not allowed in a closing tag of an element.

  • attributeList

    Optional. List of attributes declared in the literal.

    attribute [ attribute ... ]

    Each attribute has one of the following syntaxes:

    • Attribute assignment, of the form [aPrefix:]aName=aValue, where:

      Part Description
      aPrefix Optional. XML namespace prefix for the attribute. Must be a global XML namespace that is defined with an Imports statement, or a local XML namespace that is defined in this element or a parent element.
      aName Required. Name of the attribute. The format is one of the following:

      - Literal text. See Names of Declared XML Elements and Attributes.
      - Embedded expression of the form <%= aNameExp %>. The type of aNameExp must be String or a type that is implicitly convertible to xref:System.Xml.Linq.XName.
      aValue Optional. Value of the attribute. The format is one of the following:

      - Literal text, enclosed in quotation marks.
      - Embedded expression of the form <%= aValueExp %>. Any type is allowed.

    • Embedded expression of the form <%= aExp %>.

  • />

    Optional. Indicates that the element is an empty element, without content.

  • >

    Required. Ends the beginning or empty element tag.

  • elementContents

    Optional. Content of the element.

    content [ content ... ]

    Each content can be one of the following:

  • </[name]>

    Optional. Represents the closing tag for the element. The optional name parameter is not allowed when it is the result of an embedded expression.

Return Value

An xref:System.Xml.Linq.XElement object.

Remarks

You can use the XML element literal syntax to create xref:System.Xml.Linq.XElement objects in your code.

Note

An XML literal can span multiple lines without using line continuation characters. This feature enables you to copy content from an XML document and paste it directly into a Visual Basic program.

Embedded expressions of the form <%= exp %> enable you to add dynamic information to an XML element literal. For more information, see Embedded Expressions in XML.

The Visual Basic compiler converts the XML element literal into calls to the xref:System.Xml.Linq.XElement.%23ctor%2A constructor and, if it is required, the xref:System.Xml.Linq.XAttribute.%23ctor%2A constructor.

XML Namespaces

XML namespace prefixes are useful when you have to create XML literals with elements from the same namespace many times in code. You can use global XML namespace prefixes, which you define by using the Imports statement, or local prefixes, which you define by using the xmlns:xmlPrefix="xmlNamespace" attribute syntax. For more information, see Imports Statement (XML Namespace).

In accordance with the scoping rules for XML namespaces, local prefixes take precedence over global prefixes. However, if an XML literal defines an XML namespace, that namespace is not available to expressions that appear in an embedded expression. The embedded expression can access only the global XML namespace.

The Visual Basic compiler converts each global XML namespace that is used by an XML literal into a one local namespace definition in the generated code. Global XML namespaces that are not used do not appear in the generated code.

Example 1

The following example shows how to create a simple XML element that has two nested empty elements.

[!code-vbVbXMLSamples#20]

The example displays the following text. Notice that the literal preserves the structure of the empty elements.

<outer>
  <inner1></inner1>
  <inner2 />
</outer>

Example 2

The following example shows how to use embedded expressions to name an element and create attributes.

[!code-vbVbXMLSamples#21]

This code displays the following text:

<book isbn="1234" author="My Author" year="1999" title="My Book" />

Example 3

The following example declares ns as an XML namespace prefix. It then uses the prefix of the namespace to create an XML literal and displays the element's final form.

[!code-vbVbXMLSamples#22]

This code displays the following text:

<ns:outer xmlns:ns="http://SomeNamespace">
  <ns:middle xmlns:ns="http://NewNamespace">
    <ns:inner1 />
    <inner2 xmlns="http://SomeNamespace" />
  </ns:middle>
</ns:outer>

Notice that the compiler converted the prefix of the global XML namespace into a prefix definition for the XML namespace. The <ns:middle> element redefines the XML namespace prefix for the <ns:inner1> element. However, the <ns:inner2> element uses the namespace defined by the Imports statement.

See also