XmlDocument.CreateEntityReference(String) Method

Definition

Namespace:

System.Xml

Assembly:

System.Xml.ReaderWriter.dll

Source:

XmlDocument.cs

Creates an XmlEntityReference with the specified name.

public:
 virtual System::Xml::XmlEntityReference ^ CreateEntityReference(System::String ^ name);

public virtual System.Xml.XmlEntityReference CreateEntityReference (string name);

abstract member CreateEntityReference : string -> System.Xml.XmlEntityReference
override this.CreateEntityReference : string -> System.Xml.XmlEntityReference

Public Overridable Function CreateEntityReference (name As String) As XmlEntityReference

Parameters

name

String

The name of the entity reference.

Returns

XmlEntityReference

The new XmlEntityReference.

Exceptions

ArgumentException

The name is invalid (for example, names starting with'#' are invalid.)

Examples

The following example creates two entity reference nodes and inserts them into an XML document.

#using <System.Xml.dll>

using namespace System;
using namespace System::IO;
using namespace System::Xml;
int main()
{
   
   //Create the XmlDocument.
   XmlDocument^ doc = gcnew XmlDocument;
   doc->LoadXml( "<!DOCTYPE book [<!ENTITY h 'hardcover'>]><book genre='novel' ISBN='1-861001-57-5'><title>Pride And Prejudice</title><misc/></book>" );
   
   //Create an entity reference node. The child count should be 0 
   //since the node has not been expanded.
   XmlEntityReference^ entityref = doc->CreateEntityReference( "h" );
   Console::WriteLine( entityref->ChildNodes->Count );
   
   //After the node has been added to the document, its parent node
   //is set and the entity reference node is expanded.  It now has a child
   //node containing the entity replacement text. 
   doc->DocumentElement->LastChild->AppendChild( entityref );
   Console::WriteLine( entityref->FirstChild->InnerText );
   
   //Create and insert an undefined entity reference node.  When the entity
   //reference node is expanded, because the entity reference is undefined
   //the child is an empty text node.
   XmlEntityReference^ entityref2 = doc->CreateEntityReference( "p" );
   doc->DocumentElement->LastChild->AppendChild( entityref2 );
   Console::WriteLine( entityref2->FirstChild->InnerText );
}

using System;
using System.IO;
using System.Xml;

public class Sample
{
  public static void Main()
  {
    //Create the XmlDocument.
    XmlDocument doc = new XmlDocument();
    doc.LoadXml("<!DOCTYPE book [<!ENTITY h 'hardcover'>]>" +
                "<book genre='novel' ISBN='1-861001-57-5'>" +
                "<title>Pride And Prejudice</title>" +
                "<misc/>" +
                "</book>");

    //Create an entity reference node. The child count should be 0
    //since the node has not been expanded.
    XmlEntityReference entityref = doc.CreateEntityReference("h");
    Console.WriteLine(entityref.ChildNodes.Count );

    //After the node has been added to the document, its parent node
    //is set and the entity reference node is expanded.  It now has a child
    //node containing the entity replacement text.
    doc.DocumentElement.LastChild.AppendChild(entityref);
    Console.WriteLine(entityref.FirstChild.InnerText);

    //Create and insert an undefined entity reference node.  When the entity
    //reference node is expanded, because the entity reference is undefined
    //the child is an empty text node.
    XmlEntityReference entityref2 = doc.CreateEntityReference("p");
    doc.DocumentElement.LastChild.AppendChild(entityref2);
    Console.WriteLine(entityref2.FirstChild.InnerText);
  }
}

Option Explicit
Option Strict

Imports System.IO
Imports System.Xml

Public Class Sample
    
    Public Shared Sub Main()
        'Create the XmlDocument.
        Dim doc As New XmlDocument()
        doc.LoadXml("<!DOCTYPE book [<!ENTITY h 'hardcover'>]>" & _
                    "<book genre='novel' ISBN='1-861001-57-5'>"  & _
                    "<title>Pride And Prejudice</title>"  & _
                    "<misc/>"  & _
                    "</book>")
        
        'Create an entity reference node. The child count should be 0 
        'since the node has not been expanded.
        Dim entityref As XmlEntityReference = doc.CreateEntityReference("h")
        Console.WriteLine(entityref.ChildNodes.Count)
        
        'After the node has been added to the document, its parent node
        'is set and the entity reference node is expanded.  It now has a child
        'node containing the entity replacement text. 
        doc.DocumentElement.LastChild.AppendChild(entityref)
        Console.WriteLine(entityref.FirstChild.InnerText)
        
        'Create and insert an undefined entity reference node.  When the entity
        'reference node is expanded, because the entity reference is undefined
        'the child is an empty text node.
        Dim entityref2 As XmlEntityReference = doc.CreateEntityReference("p")
        doc.DocumentElement.LastChild.AppendChild(entityref2)
        Console.WriteLine(entityref2.FirstChild.InnerText)
    End Sub
End Class

Remarks

If the referenced entity is known, the child list of the XmlEntityReference node is made the same as that of the corresponding XmlEntity node.

The namespaces used in the replacement text for the entity reference are bound at the time the parent of the entity reference node is first set (for example, when the entity reference node is inserted into the document). For example, given the following entity:

<!ENTITY a "<b>test</b>">

If you call CreateEntityReference("a") you get back a single node of type EntityReference with no children. If you append this node as a child of the following node,

<item xmlns="urn:1"/>

then, at the time of calling AppendChild, the parent of the newly created entity reference node is set and the children are expanded in this namespace context. The child element node b will have NamespaceURI equal to urn:1. The child nodes of the entity reference remain the same even if you move the entity reference to a place in the document that has a different default namespace context. This does not happen for existing entity reference nodes when you remove and insert them or for entity references that you clone with CloneNode. It only happens for newly created entity references.

If the corresponding entity is not defined in the DocumentType when the entity reference node is added, because the entity reference is not defined, its only child node will be an empty text node.

The built-in entities amp, lt, gt, apos, and quot are also allowed, and they will have a child text node with the appropriate expanded character value.

Although this method creates the new object in the context of the document, it does not automatically add the new object to the document tree. To add the new object, you must explicitly call one of the node insert methods.

According to the W3C Extensible Markup Language (XML) 1.0 recommendation, EntityReference nodes are only allowed within Element, Attribute and EntityReference nodes.