XmlWriter.WriteProcessingInstruction Method
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When overridden in a derived class, writes out a processing instruction with a space between the name and text as follows: <?name text?>.
Namespace: System.Xml
Assembly: System.Xml (in System.Xml.dll)
Syntax
'Declaration
Public MustOverride Sub WriteProcessingInstruction ( _
name As String, _
text As String _
)
public abstract void WriteProcessingInstruction(
string name,
string text
)
Parameters
- name
Type: System.String
The name of the processing instruction.
- text
Type: System.String
The text to include in the processing instruction.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentException | The text would result in a non-well formed XML document. name is either nulla null reference (Nothing in Visual Basic) or String.Empty. This method is being used to create an XML declaration after WriteStartDocument has already been called. |
Remarks
This method can be used to write the XML declaration (rather than WriteStartDocument). This could result in the encoding attribute being incorrectly written. For example, the following C# code would result in an invalid XML document because the default encoding is UTF-8.
XmlWriter writer = XmlWriter.Create("output.xml");
writer.WriteProcessingInstruction("xml", "version='1.0' encoding='UTF-16'");
writer.WriteStartElement("root");
writer.Close();
If text is either nulla null reference (Nothing in Visual Basic) or String.Empty, this method writes a ProcessingInstruction with no data content, for example <?name?>.
If text contains an invalid sequence of "?>", the XmlWriter can either throw an ArgumentException or insert a space "? >" to avoid writing invalid XML (XmlWriter objects created by the Create method).
Examples
The following example navigates through the stream to determine the current node type, and then uses XmlWriter to output the XmlReader content.
Dim output As StringBuilder = New StringBuilder()
Dim xmlString As String = "<?xml version='1.0'?>" & _
"<!-- This is a sample XML document -->" & _
"<Items>" & _
"<Item>test with a child element <more/> stuff</Item>" & _
"</Items>"
' Create an XmlReader
Using reader As XmlReader = XmlReader.Create(New StringReader(xmlString))
Dim ws As XmlWriterSettings = New XmlWriterSettings()
ws.Indent = True
Using writer As XmlWriter = XmlWriter.Create(output, ws)
' Parse the file and display each of the nodes.
While reader.Read()
Select Case reader.NodeType
Case XmlNodeType.Element
writer.WriteStartElement(reader.Name)
Case XmlNodeType.Text
writer.WriteString(reader.Value)
Case XmlNodeType.XmlDeclaration
Case XmlNodeType.ProcessingInstruction
writer.WriteProcessingInstruction(reader.Name, reader.Value)
Case XmlNodeType.Comment
writer.WriteComment(reader.Value)
Case XmlNodeType.EndElement
writer.WriteFullEndElement()
End Select
End While
End Using
End Using
OutputTextBlock.Text = output.ToString()
StringBuilder output = new StringBuilder();
String xmlString =
@"<?xml version='1.0'?>
<!-- This is a sample XML document -->
<Items>
<Item>test with a child element <more/> stuff</Item>
</Items>";
// Create an XmlReader
using (XmlReader reader = XmlReader.Create(new StringReader(xmlString)))
{
XmlWriterSettings ws = new XmlWriterSettings();
ws.Indent = true;
using (XmlWriter writer = XmlWriter.Create(output, ws))
{
// Parse the file and display each of the nodes.
while (reader.Read())
{
switch (reader.NodeType)
{
case XmlNodeType.Element:
writer.WriteStartElement(reader.Name);
break;
case XmlNodeType.Text:
writer.WriteString(reader.Value);
break;
case XmlNodeType.XmlDeclaration:
case XmlNodeType.ProcessingInstruction:
writer.WriteProcessingInstruction(reader.Name, reader.Value);
break;
case XmlNodeType.Comment:
writer.WriteComment(reader.Value);
break;
case XmlNodeType.EndElement:
writer.WriteFullEndElement();
break;
}
}
}
}
OutputTextBlock.Text = output.ToString();
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
See Also