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XmlWriter.WriteStartElement Method (String, String, String)


When overridden in a derived class, writes the specified start tag and associates it with the given namespace and prefix.

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

public abstract void WriteStartElement(
	string prefix,
	string localName,
	string ns


Type: System.String

The namespace prefix of the element.

Type: System.String

The local name of the element.

Type: System.String

The namespace URI to associate with the element.

Exception Condition

The writer is closed.


There is a character in the buffer that is a valid XML character but is not valid for the output encoding. For example, if the output encoding is ASCII, you should only use characters from the range of 0 to 127 for element and attribute names. The invalid character might be in the argument of this method or in an argument of previous methods that were writing to the buffer. Such characters are escaped by character entity references when possible (for example, in text nodes or attribute values). However, the character entity reference is not allowed in element and attribute names, comments, processing instructions, or CDATA sections.


An XmlWriter method was called before a previous asynchronous operation finished. In this case, InvalidOperationException is thrown with the message “An asynchronous operation is already in progress.”

For the asynchronous version of this method, see WriteStartElementAsync.

The following example writes out an XML fragment.

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

 public class Sample
   private const string m_Document = "sampledata.xml";

   public static void Main() {

      XmlWriter writer = null;

      try {

        XmlWriterSettings settings = new XmlWriterSettings();
        settings.Indent = true;
        writer = XmlWriter.Create (m_Document, settings);

        writer.WriteComment("sample XML fragment");

        // Write an element (this one is the root).

        // Write the namespace declaration.
        writer.WriteAttributeString("xmlns", "bk", null, "urn:samples");

        // Write the genre attribute.
        writer.WriteAttributeString("genre", "novel");

        // Write the title.
        writer.WriteString("The Handmaid's Tale");

        // Write the price.
        writer.WriteElementString("price", "19.95");

        // Lookup the prefix and write the ISBN element.
        string prefix = writer.LookupPrefix("urn:samples");
        writer.WriteStartElement(prefix, "ISBN", "urn:samples");

        // Write the style element (shows a different way to handle prefixes).
        writer.WriteElementString("style", "urn:samples", "hardcover");

        // Write the close tag for the root element.

        // Write the XML to file and close the writer.

      finally {
        if (writer != null)


Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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