XmlNamespaceManager.LookupPrefix(String) Method

Definition

Namespace:

System.Xml

Assembly:

System.Xml.ReaderWriter.dll

Source:

XmlNamespacemanager.cs

Finds the prefix declared for the given namespace URI.

public:
 virtual System::String ^ LookupPrefix(System::String ^ uri);

public virtual string? LookupPrefix (string uri);

abstract member LookupPrefix : string -> string
override this.LookupPrefix : string -> string

Public Overridable Function LookupPrefix (uri As String) As String

Parameters

uri

String

The namespace to resolve for the prefix.

Returns

String

The matching prefix. If there is no mapped prefix, the method returns String.Empty. If a null value is supplied, then null is returned.

Implements

LookupPrefix(String)

Examples

The following example shows how to use the LookupPrefix method when writing an attribute. It uses the XmlWriter.WriteStartAttribute method to start the attribute, looks up the prefix for the urn:samples namespace URI, and then uses that prefix in the XmlWriter.WriteStartAttribute when writing the ISBN attribute:

Dim prefix As String = nsMgr.LookupPrefix("urn:samples")  
writer.WriteStartAttribute(prefix, "ISBN", "urn:samples")  

XmlNameTable nt = new XmlNameTable();  
XmlNamespaceManager nsMgr = new XmlNamespaceManager(nt);  
nsMgr.AddNamespace("bk","urn:samples");string prefix = writer nsMgr.LookupPrefix("urn:samples");  
writer.WriteStartAttribute(prefix, "ISBN", "urn:samples");  

The following example uses LookupPrefix to find the prefix defined on an element.

writer.WriteStartElement("root", "book")  
writer.WriteStartElement("x", "node", "author")  
s = writer.LookupPrefix("author")  
CError.Compare(s, "x", "Error in nested element")  
writer.WriteEndElement()  
s = writer.LookupPrefix("book")  
CError.Compare(s, Nothing, "Error in root element")  
writer.WriteEndElement()  

Output

<root xmlns="book">  
  <x:node xmlns:x="author" />   
</root>  

Remarks

This method finds the mapped prefix by walking the stack (that is, it looks globally). The supplied string must be atomized for the lookup to succeed. In other words, the supplied string object must exist in the namespace manager's name table (NameTable).

The returned string is also atomized. For more information on atomized strings, see the XmlNameTable class.

See also

• LookupNamespace(String)
• XML Documents and Data
• Managing Namespaces in an XML Document