XmlTextWriter.LookupPrefix Method
.NET Framework 4
Returns the closest prefix defined in the current namespace scope for the namespace URI.
Assembly: System.Xml (in System.Xml.dll)
Parameters
- ns
- Type: System.String
Namespace URI whose prefix you want to find.
Return Value
Type: System.StringThe matching prefix. Or null if no matching namespace URI is found in the current scope.
| Exception | Condition |
|---|---|
| ArgumentException |
ns is either null or String.Empty. |
Note
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In the .NET Framework version 2.0 release, the recommended practice is to create XmlWriter instances using the XmlWriter.Create method and the XmlWriterSettings class. This allows you to take full advantage of all the new features introduced in this release. For more information, see Creating XML Writers. |
The following example writes out a book.
using System; using System.IO; using System.Xml; public class Sample { private const string filename = "sampledata.xml"; public static void Main() { XmlTextWriter writer = new XmlTextWriter (filename, null); //Use indenting for readability. writer.Formatting = Formatting.Indented; writer.WriteComment("sample XML fragment"); //Write an element (this one is the root). writer.WriteStartElement("bookstore"); //Write the namespace declaration. writer.WriteAttributeString("xmlns", "bk", null, "urn:samples"); writer.WriteStartElement("book"); //Lookup the prefix and then write the ISBN attribute. string prefix = writer.LookupPrefix("urn:samples"); writer.WriteStartAttribute(prefix, "ISBN", "urn:samples"); writer.WriteString("1-861003-78"); writer.WriteEndAttribute(); //Write the title. writer.WriteStartElement("title"); writer.WriteString("The Handmaid's Tale"); writer.WriteEndElement(); //Write the price. writer.WriteElementString("price", "19.95"); //Write the style element. writer.WriteStartElement(prefix, "style", "urn:samples"); writer.WriteString("hardcover"); writer.WriteEndElement(); //Write the end tag for the book element. writer.WriteEndElement(); //Write the close tag for the root element. writer.WriteEndElement(); //Write the XML to file and close the writer. writer.Flush(); writer.Close(); //Read the file back in and parse to ensure well formed XML. XmlDocument doc = new XmlDocument(); //Preserve white space for readability. doc.PreserveWhitespace = true; //Load the file doc.Load(filename); //Write the XML content to the console. Console.Write(doc.InnerXml); } }
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
